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	$152.94	10.306%	$168.702	$168.70	$168.70	$168.70
Purchase #2	$41.78	7.431%	$44.8847	$44.88	$44.90	$44.90
Purchase #3	$225.62	10.317%	$248.8972	$248.90	$248.90	$248.90
Purchase #4	$198.98	13.541%	$225.9239	$225.92	$225.90	$225.90
Purchase #5	$177.88	7.690%	$191.559	$191.56	$191.55	$191.60
Purchase #6	$177.98	10.390%	$196.4721	$196.47	$196.45	$196.50
Purchase #7	$145.84	8.550%	$158.3093	$158.31	$158.30	$158.30
7 purchase totals =	$1,121.02		$1,234.7482	$1,234.74	$1,234.70	$1,234.80