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	$59.63	4.278%	$62.181	$62.18	$62.20	$62.20
Purchase #2	$175.78	8.575%	$190.8531	$190.85	$190.85	$190.90
Purchase #3	$66.33	8.816%	$72.1777	$72.18	$72.20	$72.20
Purchase #4	$203.34	5.316%	$214.1496	$214.15	$214.15	$214.10
Purchase #5	$180.76	3.562%	$187.1987	$187.20	$187.20	$187.20
Purchase #6	$172.69	13.583%	$196.1465	$196.15	$196.15	$196.10
Purchase #7	$68.34	4.499%	$71.4146	$71.41	$71.40	$71.40
7 purchase totals =	$926.87		$994.1212	$994.12	$994.15	$994.10