Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$102.70	7.838%	$110.7496	$110.75	$110.75	$110.70
Purchase #2	$173.69	13.148%	$196.5268	$196.53	$196.55	$196.50
Purchase #3	$185.91	10.474%	$205.3822	$205.38	$205.40	$205.40
Purchase #4	$240.31	10.118%	$264.6246	$264.62	$264.60	$264.60
Purchase #5	$138.38	10.285%	$152.6124	$152.61	$152.60	$152.60
Purchase #6	$123.45	3.547%	$127.8288	$127.83	$127.85	$127.80
Purchase #7	$108.55	11.254%	$120.7662	$120.77	$120.75	$120.80
7 purchase totals =	$1,072.99		$1,178.4906	$1,178.49	$1,178.50	$1,178.40