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	$100.42	4.839%	$105.2793	$105.28	$105.30	$105.30
Purchase #2	$191.50	5.795%	$202.5974	$202.60	$202.60	$202.60
Purchase #3	$222.89	7.823%	$240.3267	$240.33	$240.35	$240.30
Purchase #4	$93.82	10.181%	$103.3718	$103.37	$103.35	$103.40
Purchase #5	$243.62	5.842%	$257.8523	$257.85	$257.85	$257.90
Purchase #6	$153.74	11.818%	$171.909	$171.91	$171.90	$171.90
Purchase #7	$154.68	11.456%	$172.4001	$172.40	$172.40	$172.40
7 purchase totals =	$1,160.67		$1,253.7366	$1,253.74	$1,253.75	$1,253.80