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	$80.62	11.183%	$89.6357	$89.64	$89.65	$89.60
Purchase #2	$210.45	5.662%	$222.3657	$222.37	$222.35	$222.40
Purchase #3	$36.82	12.641%	$41.4744	$41.47	$41.45	$41.50
Purchase #4	$154.58	9.737%	$169.6315	$169.63	$169.65	$169.60
Purchase #5	$158.95	7.735%	$171.2448	$171.24	$171.25	$171.20
Purchase #6	$217.88	5.812%	$230.5432	$230.54	$230.55	$230.50
Purchase #7	$248.77	10.597%	$275.1322	$275.13	$275.15	$275.10
7 purchase totals =	$1,108.07		$1,200.0275	$1,200.02	$1,200.05	$1,199.90