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	$246.53	9.480%	$269.901	$269.90	$269.90	$269.90
Purchase #2	$61.55	9.608%	$67.4637	$67.46	$67.45	$67.50
Purchase #3	$203.45	3.633%	$210.8413	$210.84	$210.85	$210.80
Purchase #4	$67.55	9.144%	$73.7268	$73.73	$73.75	$73.70
Purchase #5	$66.42	10.385%	$73.3177	$73.32	$73.30	$73.30
Purchase #6	$191.92	9.849%	$210.8222	$210.82	$210.80	$210.80
Purchase #7	$40.38	12.417%	$45.394	$45.39	$45.40	$45.40
7 purchase totals =	$877.80		$951.4667	$951.46	$951.45	$951.40