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	$40.88	13.302%	$46.3179	$46.32	$46.30	$46.30
Purchase #2	$60.52	11.868%	$67.7025	$67.70	$67.70	$67.70
Purchase #3	$82.35	5.600%	$86.9616	$86.96	$86.95	$87.00
Purchase #4	$79.46	5.453%	$83.793	$83.79	$83.80	$83.80
Purchase #5	$147.73	8.159%	$159.7833	$159.78	$159.80	$159.80
Purchase #6	$225.46	13.176%	$255.1666	$255.17	$255.15	$255.20
Purchase #7	$208.38	3.521%	$215.7171	$215.72	$215.70	$215.70
7 purchase totals =	$844.78		$915.4420	$915.44	$915.40	$915.50