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	$120.29	9.492%	$131.7079	$131.71	$131.70	$131.70
Purchase #2	$21.63	3.102%	$22.301	$22.30	$22.30	$22.30
Purchase #3	$195.61	13.742%	$222.4907	$222.49	$222.50	$222.50
Purchase #4	$202.75	7.841%	$218.6476	$218.65	$218.65	$218.60
Purchase #5	$172.33	8.389%	$186.7868	$186.79	$186.80	$186.80
Purchase #6	$96.55	3.433%	$99.8646	$99.86	$99.85	$99.90
Purchase #7	$104.98	9.223%	$114.6623	$114.66	$114.65	$114.70
7 purchase totals =	$914.14		$996.4609	$996.46	$996.45	$996.50