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	$222.89	10.293%	$245.8321	$245.83	$245.85	$245.80
Purchase #2	$170.83	10.370%	$188.5451	$188.55	$188.55	$188.50
Purchase #3	$163.64	9.516%	$179.212	$179.21	$179.20	$179.20
Purchase #4	$114.69	3.311%	$118.4874	$118.49	$118.50	$118.50
Purchase #5	$187.88	4.580%	$196.4849	$196.48	$196.50	$196.50
Purchase #6	$182.39	6.231%	$193.7547	$193.75	$193.75	$193.80
Purchase #7	$135.72	11.384%	$151.1704	$151.17	$151.15	$151.20
7 purchase totals =	$1,178.04		$1,273.4866	$1,273.48	$1,273.50	$1,273.50