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	$250.41	7.228%	$268.5096	$268.51	$268.50	$268.50
Purchase #2	$162.87	13.740%	$185.2483	$185.25	$185.25	$185.20
Purchase #3	$74.30	10.850%	$82.3616	$82.36	$82.35	$82.40
Purchase #4	$145.52	9.435%	$159.2498	$159.25	$159.25	$159.20
Purchase #5	$21.69	4.650%	$22.6986	$22.70	$22.70	$22.70
Purchase #6	$172.73	3.760%	$179.2246	$179.22	$179.20	$179.20
Purchase #7	$110.85	8.122%	$119.8532	$119.85	$119.85	$119.90
7 purchase totals =	$938.37		$1,017.1457	$1,017.14	$1,017.10	$1,017.10