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	$166.45	12.430%	$187.1397	$187.14	$187.15	$187.10
Purchase #2	$54.95	3.344%	$56.7875	$56.79	$56.80	$56.80
Purchase #3	$107.83	3.353%	$111.4455	$111.45	$111.45	$111.40
Purchase #4	$36.73	11.442%	$40.9326	$40.93	$40.95	$40.90
Purchase #5	$58.87	6.506%	$62.7001	$62.70	$62.70	$62.70
Purchase #6	$234.46	4.778%	$245.6625	$245.66	$245.65	$245.70
Purchase #7	$212.88	11.826%	$238.0552	$238.06	$238.05	$238.10
7 purchase totals =	$872.17		$942.7231	$942.73	$942.75	$942.70