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	$88.79	11.385%	$98.8987	$98.90	$98.90	$98.90
Purchase #2	$64.27	11.309%	$71.5383	$71.54	$71.55	$71.50
Purchase #3	$175.38	12.192%	$196.7623	$196.76	$196.75	$196.80
Purchase #4	$207.76	6.252%	$220.7492	$220.75	$220.75	$220.70
Purchase #5	$229.32	6.335%	$243.8474	$243.85	$243.85	$243.80
Purchase #6	$172.54	12.505%	$194.1161	$194.12	$194.10	$194.10
Purchase #7	$146.30	13.196%	$165.6057	$165.61	$165.60	$165.60
7 purchase totals =	$1,084.36		$1,191.5177	$1,191.53	$1,191.50	$1,191.40