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	$179.96	7.434%	$193.3382	$193.34	$193.35	$193.30
Purchase #2	$67.66	4.620%	$70.7859	$70.79	$70.80	$70.80
Purchase #3	$52.72	5.745%	$55.7488	$55.75	$55.75	$55.70
Purchase #4	$136.84	3.302%	$141.3585	$141.36	$141.35	$141.40
Purchase #5	$203.31	11.627%	$226.9489	$226.95	$226.95	$226.90
Purchase #6	$145.91	12.582%	$164.2684	$164.27	$164.25	$164.30
Purchase #7	$145.87	3.815%	$151.4349	$151.43	$151.45	$151.40
7 purchase totals =	$932.27		$1,003.8836	$1,003.89	$1,003.90	$1,003.80