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	$175.90	3.154%	$181.4479	$181.45	$181.45	$181.40
Purchase #2	$211.87	10.775%	$234.699	$234.70	$234.70	$234.70
Purchase #3	$19.27	6.452%	$20.5133	$20.51	$20.50	$20.50
Purchase #4	$111.87	10.172%	$123.2494	$123.25	$123.25	$123.20
Purchase #5	$227.28	11.628%	$253.7081	$253.71	$253.70	$253.70
Purchase #6	$114.89	11.263%	$127.8301	$127.83	$127.85	$127.80
Purchase #7	$155.54	8.154%	$168.2227	$168.22	$168.20	$168.20
7 purchase totals =	$1,016.62		$1,109.6705	$1,109.67	$1,109.65	$1,109.50