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	$21.27	6.517%	$22.6562	$22.66	$22.65	$22.70
Purchase #2	$86.68	8.525%	$94.0695	$94.07	$94.05	$94.10
Purchase #3	$227.42	13.478%	$258.0717	$258.07	$258.05	$258.10
Purchase #4	$59.83	12.687%	$67.4206	$67.42	$67.40	$67.40
Purchase #5	$249.89	12.654%	$281.5111	$281.51	$281.50	$281.50
Purchase #6	$152.61	10.190%	$168.161	$168.16	$168.15	$168.20
Purchase #7	$150.89	6.260%	$160.3357	$160.34	$160.35	$160.30
7 purchase totals =	$948.59		$1,052.2258	$1,052.23	$1,052.15	$1,052.30