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	$36.60	13.411%	$41.5084	$41.51	$41.50	$41.50
Purchase #2	$88.46	13.194%	$100.1314	$100.13	$100.15	$100.10
Purchase #3	$69.54	9.775%	$76.3375	$76.34	$76.35	$76.30
Purchase #4	$96.86	3.343%	$100.098	$100.10	$100.10	$100.10
Purchase #5	$92.53	12.621%	$104.2082	$104.21	$104.20	$104.20
Purchase #6	$91.91	5.254%	$96.739	$96.74	$96.75	$96.70
Purchase #7	$234.89	5.729%	$248.3468	$248.35	$248.35	$248.30
7 purchase totals =	$710.79		$767.3693	$767.38	$767.40	$767.20