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	$190.86	3.553%	$197.6413	$197.64	$197.65	$197.60
Purchase #2	$101.64	3.421%	$105.1171	$105.12	$105.10	$105.10
Purchase #3	$20.37	6.198%	$21.6325	$21.63	$21.65	$21.60
Purchase #4	$188.61	9.492%	$206.5129	$206.51	$206.50	$206.50
Purchase #5	$69.49	13.592%	$78.9351	$78.94	$78.95	$78.90
Purchase #6	$53.61	13.396%	$60.7916	$60.79	$60.80	$60.80
Purchase #7	$157.41	5.384%	$165.885	$165.89	$165.90	$165.90
7 purchase totals =	$781.99		$836.5155	$836.52	$836.55	$836.40