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	$9.96	13.751%	$11.3296	$11.33	$11.35	$11.30
Purchase #2	$172.92	7.297%	$185.538	$185.54	$185.55	$185.50
Purchase #3	$96.40	5.852%	$102.0413	$102.04	$102.05	$102.00
Purchase #4	$229.34	9.251%	$250.5562	$250.56	$250.55	$250.60
Purchase #5	$86.63	11.532%	$96.6202	$96.62	$96.60	$96.60
Purchase #6	$240.45	7.465%	$258.3996	$258.40	$258.40	$258.40
Purchase #7	$152.56	9.867%	$167.6131	$167.61	$167.60	$167.60
7 purchase totals =	$988.26		$1,072.0980	$1,072.10	$1,072.10	$1,072.00