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	$126.65	8.651%	$137.6065	$137.61	$137.60	$137.60
Purchase #2	$165.75	4.744%	$173.6132	$173.61	$173.60	$173.60
Purchase #3	$111.55	7.541%	$119.962	$119.96	$119.95	$120.00
Purchase #4	$188.27	4.373%	$196.503	$196.50	$196.50	$196.50
Purchase #5	$211.98	8.178%	$229.3157	$229.32	$229.30	$229.30
Purchase #6	$21.35	12.747%	$24.0715	$24.07	$24.05	$24.10
Purchase #7	$145.69	9.653%	$159.7535	$159.75	$159.75	$159.80
7 purchase totals =	$971.24		$1,040.8254	$1,040.82	$1,040.75	$1,040.90