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	$49.72	6.660%	$53.0314	$53.03	$53.05	$53.00
Purchase #2	$207.83	6.447%	$221.2288	$221.23	$221.25	$221.20
Purchase #3	$36.75	3.234%	$37.9385	$37.94	$37.95	$37.90
Purchase #4	$211.76	12.797%	$238.8589	$238.86	$238.85	$238.90
Purchase #5	$222.98	9.181%	$243.4518	$243.45	$243.45	$243.50
Purchase #6	$246.37	11.806%	$275.4564	$275.46	$275.45	$275.50
Purchase #7	$79.33	4.238%	$82.692	$82.69	$82.70	$82.70
7 purchase totals =	$1,054.74		$1,152.6578	$1,152.66	$1,152.70	$1,152.70