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	$102.29	4.516%	$106.9094	$106.91	$106.90	$106.90
Purchase #2	$215.72	3.300%	$222.8388	$222.84	$222.85	$222.80
Purchase #3	$89.45	9.734%	$98.1571	$98.16	$98.15	$98.20
Purchase #4	$231.82	6.338%	$246.5128	$246.51	$246.50	$246.50
Purchase #5	$219.49	13.542%	$249.2133	$249.21	$249.20	$249.20
Purchase #6	$164.95	6.415%	$175.5315	$175.53	$175.55	$175.50
Purchase #7	$30.25	6.187%	$32.1216	$32.12	$32.10	$32.10
7 purchase totals =	$1,053.97		$1,131.2845	$1,131.28	$1,131.25	$1,131.20