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	$104.86	13.757%	$119.2856	$119.29	$119.30	$119.30
Purchase #2	$202.41	12.489%	$227.689	$227.69	$227.70	$227.70
Purchase #3	$89.35	13.607%	$101.5079	$101.51	$101.50	$101.50
Purchase #4	$203.66	6.283%	$216.456	$216.46	$216.45	$216.50
Purchase #5	$90.68	9.621%	$99.4043	$99.40	$99.40	$99.40
Purchase #6	$116.53	8.727%	$126.6996	$126.70	$126.70	$126.70
Purchase #7	$165.69	6.159%	$175.8948	$175.89	$175.90	$175.90
7 purchase totals =	$973.18		$1,066.9372	$1,066.94	$1,066.95	$1,067.00