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	$203.37	4.375%	$212.2674	$212.27	$212.25	$212.30
Purchase #2	$75.40	3.443%	$77.996	$78.00	$78.00	$78.00
Purchase #3	$190.72	4.781%	$199.8383	$199.84	$199.85	$199.80
Purchase #4	$51.83	6.305%	$55.0979	$55.10	$55.10	$55.10
Purchase #5	$222.93	10.297%	$245.8851	$245.89	$245.90	$245.90
Purchase #6	$65.37	8.642%	$71.0193	$71.02	$71.00	$71.00
Purchase #7	$195.58	10.778%	$216.6596	$216.66	$216.65	$216.70
7 purchase totals =	$1,005.20		$1,078.7636	$1,078.78	$1,078.75	$1,078.80