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	$210.73	11.662%	$235.3053	$235.31	$235.30	$235.30
Purchase #2	$250.38	11.490%	$279.1487	$279.15	$279.15	$279.10
Purchase #3	$244.40	10.274%	$269.5097	$269.51	$269.50	$269.50
Purchase #4	$46.96	6.146%	$49.8462	$49.85	$49.85	$49.80
Purchase #5	$55.65	6.601%	$59.3235	$59.32	$59.30	$59.30
Purchase #6	$7.90	7.768%	$8.5137	$8.51	$8.50	$8.50
Purchase #7	$175.55	5.135%	$184.5645	$184.56	$184.55	$184.60
7 purchase totals =	$991.57		$1,086.2116	$1,086.21	$1,086.15	$1,086.10