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	$238.59	5.167%	$250.9179	$250.92	$250.90	$250.90
Purchase #2	$249.88	11.628%	$278.936	$278.94	$278.95	$278.90
Purchase #3	$151.49	7.188%	$162.3791	$162.38	$162.40	$162.40
Purchase #4	$54.62	8.390%	$59.2026	$59.20	$59.20	$59.20
Purchase #5	$216.66	9.841%	$237.9815	$237.98	$238.00	$238.00
Purchase #6	$168.52	6.353%	$179.2261	$179.23	$179.25	$179.20
Purchase #7	$82.46	4.433%	$86.1155	$86.12	$86.10	$86.10
7 purchase totals =	$1,162.22		$1,254.7587	$1,254.77	$1,254.80	$1,254.70