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	$167.29	8.840%	$182.0784	$182.08	$182.10	$182.10
Purchase #2	$79.59	12.501%	$89.5395	$89.54	$89.55	$89.50
Purchase #3	$53.77	6.352%	$57.1855	$57.19	$57.20	$57.20
Purchase #4	$150.28	13.220%	$170.147	$170.15	$170.15	$170.10
Purchase #5	$106.72	4.399%	$111.4146	$111.41	$111.40	$111.40
Purchase #6	$242.61	9.682%	$266.0995	$266.10	$266.10	$266.10
Purchase #7	$26.51	3.838%	$27.5275	$27.53	$27.55	$27.50
7 purchase totals =	$826.77		$903.9920	$904.00	$904.05	$903.90