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	$48.96	11.625%	$54.6516	$54.65	$54.65	$54.70
Purchase #2	$83.30	7.508%	$89.5542	$89.55	$89.55	$89.60
Purchase #3	$169.49	11.683%	$189.2915	$189.29	$189.30	$189.30
Purchase #4	$36.87	6.496%	$39.2651	$39.27	$39.25	$39.30
Purchase #5	$83.70	12.487%	$94.1516	$94.15	$94.15	$94.20
Purchase #6	$142.75	9.323%	$156.0586	$156.06	$156.05	$156.10
Purchase #7	$65.94	11.164%	$73.3015	$73.30	$73.30	$73.30
7 purchase totals =	$631.01		$696.2741	$696.27	$696.25	$696.50