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	$122.35	7.113%	$131.0528	$131.05	$131.05	$131.10
Purchase #2	$137.97	5.874%	$146.0744	$146.07	$146.05	$146.10
Purchase #3	$110.94	5.179%	$116.6856	$116.69	$116.70	$116.70
Purchase #4	$52.88	6.111%	$56.1115	$56.11	$56.10	$56.10
Purchase #5	$66.61	7.720%	$71.7523	$71.75	$71.75	$71.80
Purchase #6	$93.81	10.232%	$103.4086	$103.41	$103.40	$103.40
Purchase #7	$78.30	7.137%	$83.8883	$83.89	$83.90	$83.90
7 purchase totals =	$662.86		$708.9735	$708.97	$708.95	$709.10