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	$92.88	6.539%	$98.9534	$98.95	$98.95	$99.00
Purchase #2	$75.49	8.859%	$82.1777	$82.18	$82.20	$82.20
Purchase #3	$15.29	6.738%	$16.3202	$16.32	$16.30	$16.30
Purchase #4	$137.73	3.279%	$142.2462	$142.25	$142.25	$142.20
Purchase #5	$111.39	5.499%	$117.5153	$117.52	$117.50	$117.50
Purchase #6	$175.70	5.354%	$185.107	$185.11	$185.10	$185.10
Purchase #7	$246.42	3.849%	$255.9047	$255.90	$255.90	$255.90
7 purchase totals =	$854.90		$898.2245	$898.23	$898.20	$898.20