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	$129.52	9.398%	$141.6923	$141.69	$141.70	$141.70
Purchase #2	$142.31	6.304%	$151.2812	$151.28	$151.30	$151.30
Purchase #3	$67.70	3.663%	$70.1799	$70.18	$70.20	$70.20
Purchase #4	$197.43	12.840%	$222.78	$222.78	$222.80	$222.80
Purchase #5	$173.88	3.139%	$179.3381	$179.34	$179.35	$179.30
Purchase #6	$74.43	10.554%	$82.2853	$82.29	$82.30	$82.30
Purchase #7	$136.90	7.465%	$147.1196	$147.12	$147.10	$147.10
7 purchase totals =	$922.17		$994.6764	$994.68	$994.75	$994.70