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	$89.34	10.348%	$98.5849	$98.58	$98.60	$98.60
Purchase #2	$42.31	4.722%	$44.3079	$44.31	$44.30	$44.30
Purchase #3	$118.76	4.495%	$124.0983	$124.10	$124.10	$124.10
Purchase #4	$13.35	8.613%	$14.4998	$14.50	$14.50	$14.50
Purchase #5	$56.54	8.846%	$61.5415	$61.54	$61.55	$61.50
Purchase #6	$81.41	13.500%	$92.4004	$92.40	$92.40	$92.40
Purchase #7	$38.46	4.154%	$40.0576	$40.06	$40.05	$40.10
7 purchase totals =	$440.17		$475.4904	$475.49	$475.50	$475.50