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	$53.98	10.348%	$59.5659	$59.57	$59.55	$59.60
Purchase #2	$69.36	12.207%	$77.8268	$77.83	$77.85	$77.80
Purchase #3	$195.25	10.490%	$215.7317	$215.73	$215.75	$215.70
Purchase #4	$20.74	11.604%	$23.1467	$23.15	$23.15	$23.10
Purchase #5	$41.68	11.573%	$46.5036	$46.50	$46.50	$46.50
Purchase #6	$66.69	7.655%	$71.7951	$71.80	$71.80	$71.80
Purchase #7	$118.26	11.557%	$131.9273	$131.93	$131.95	$131.90
7 purchase totals =	$565.96		$626.4971	$626.51	$626.55	$626.40