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	$100.61	3.645%	$104.2772	$104.28	$104.30	$104.30
Purchase #2	$9.89	9.192%	$10.7991	$10.80	$10.80	$10.80
Purchase #3	$41.77	4.385%	$43.6016	$43.60	$43.60	$43.60
Purchase #4	$113.93	11.830%	$127.4079	$127.41	$127.40	$127.40
Purchase #5	$54.34	7.874%	$58.6187	$58.62	$58.60	$58.60
Purchase #6	$135.97	7.618%	$146.3282	$146.33	$146.35	$146.30
Purchase #7	$149.46	6.740%	$159.5336	$159.53	$159.55	$159.50
7 purchase totals =	$605.97		$650.5663	$650.57	$650.60	$650.50