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	$250.92	10.512%	$277.2967	$277.30	$277.30	$277.30
Purchase #2	$88.90	13.326%	$100.7468	$100.75	$100.75	$100.70
Purchase #3	$51.58	7.696%	$55.5496	$55.55	$55.55	$55.50
Purchase #4	$62.96	11.722%	$70.3402	$70.34	$70.35	$70.30
Purchase #5	$218.56	4.450%	$228.2859	$228.29	$228.30	$228.30
Purchase #6	$85.33	5.599%	$90.1076	$90.11	$90.10	$90.10
Purchase #7	$217.65	3.511%	$225.2917	$225.29	$225.30	$225.30
7 purchase totals =	$975.90		$1,047.6185	$1,047.63	$1,047.65	$1,047.50