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	$57.45	7.301%	$61.6444	$61.64	$61.65	$61.60
Purchase #2	$71.32	10.402%	$78.7387	$78.74	$78.75	$78.70
Purchase #3	$53.88	13.455%	$61.1296	$61.13	$61.15	$61.10
Purchase #4	$206.91	7.153%	$221.7103	$221.71	$221.70	$221.70
Purchase #5	$201.28	12.740%	$226.9231	$226.92	$226.90	$226.90
Purchase #6	$101.38	12.275%	$113.8244	$113.82	$113.80	$113.80
Purchase #7	$149.92	10.401%	$165.5132	$165.51	$165.50	$165.50
7 purchase totals =	$842.14		$929.4837	$929.47	$929.45	$929.30