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	$46.51	12.300%	$52.2307	$52.23	$52.25	$52.20
Purchase #2	$26.30	4.266%	$27.422	$27.42	$27.40	$27.40
Purchase #3	$84.53	7.489%	$90.8605	$90.86	$90.85	$90.90
Purchase #4	$249.73	5.777%	$264.1569	$264.16	$264.15	$264.20
Purchase #5	$13.40	8.170%	$14.4948	$14.49	$14.50	$14.50
Purchase #6	$28.60	10.809%	$31.6914	$31.69	$31.70	$31.70
Purchase #7	$152.71	10.109%	$168.1475	$168.15	$168.15	$168.10
7 purchase totals =	$601.78		$649.0038	$649.00	$649.00	$649.00