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	$50.75	5.559%	$53.5712	$53.57	$53.55	$53.60
Purchase #2	$73.62	5.258%	$77.4909	$77.49	$77.50	$77.50
Purchase #3	$225.64	9.700%	$247.5271	$247.53	$247.55	$247.50
Purchase #4	$134.66	7.104%	$144.2262	$144.23	$144.25	$144.20
Purchase #5	$219.60	7.826%	$236.7859	$236.79	$236.80	$236.80
Purchase #6	$64.83	12.174%	$72.7224	$72.72	$72.70	$72.70
Purchase #7	$103.80	6.546%	$110.5947	$110.59	$110.60	$110.60
7 purchase totals =	$872.90		$942.9184	$942.92	$942.95	$942.90