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	$206.51	8.252%	$223.5512	$223.55	$223.55	$223.60
Purchase #2	$95.46	4.489%	$99.7452	$99.75	$99.75	$99.70
Purchase #3	$155.39	12.180%	$174.3165	$174.32	$174.30	$174.30
Purchase #4	$171.51	11.407%	$191.0741	$191.07	$191.05	$191.10
Purchase #5	$73.49	6.689%	$78.4057	$78.41	$78.40	$78.40
Purchase #6	$41.56	6.616%	$44.3096	$44.31	$44.30	$44.30
Purchase #7	$166.79	8.731%	$181.3524	$181.35	$181.35	$181.40
7 purchase totals =	$910.71		$992.7547	$992.76	$992.70	$992.80