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	$165.81	13.175%	$187.6555	$187.66	$187.65	$187.70
Purchase #2	$53.35	8.379%	$57.8202	$57.82	$57.80	$57.80
Purchase #3	$223.75	5.529%	$236.1211	$236.12	$236.10	$236.10
Purchase #4	$183.64	9.159%	$200.4596	$200.46	$200.45	$200.50
Purchase #5	$84.50	9.412%	$92.4531	$92.45	$92.45	$92.50
Purchase #6	$198.42	5.442%	$209.218	$209.22	$209.20	$209.20
Purchase #7	$94.47	6.830%	$100.9223	$100.92	$100.90	$100.90
7 purchase totals =	$1,003.94		$1,084.6498	$1,084.65	$1,084.55	$1,084.70