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	$64.78	5.378%	$68.2639	$68.26	$68.25	$68.30
Purchase #2	$231.49	12.123%	$259.5535	$259.55	$259.55	$259.60
Purchase #3	$124.39	5.175%	$130.8272	$130.83	$130.85	$130.80
Purchase #4	$185.86	5.590%	$196.2496	$196.25	$196.25	$196.20
Purchase #5	$33.51	10.112%	$36.8985	$36.90	$36.90	$36.90
Purchase #6	$245.76	4.431%	$256.6496	$256.65	$256.65	$256.60
Purchase #7	$77.69	4.219%	$80.9677	$80.97	$80.95	$81.00
7 purchase totals =	$963.48		$1,029.4100	$1,029.41	$1,029.40	$1,029.40