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	$47.81	9.519%	$52.361	$52.36	$52.35	$52.40
Purchase #2	$103.76	12.122%	$116.3378	$116.34	$116.35	$116.30
Purchase #3	$155.29	8.795%	$168.9478	$168.95	$168.95	$168.90
Purchase #4	$38.27	5.783%	$40.4832	$40.48	$40.50	$40.50
Purchase #5	$245.89	3.324%	$254.0634	$254.06	$254.05	$254.10
Purchase #6	$148.85	11.564%	$166.063	$166.06	$166.05	$166.10
Purchase #7	$175.98	7.108%	$188.4887	$188.49	$188.50	$188.50
7 purchase totals =	$915.85		$986.7449	$986.74	$986.75	$986.80