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	$232.56	3.656%	$241.0624	$241.06	$241.05	$241.10
Purchase #2	$48.62	7.126%	$52.0847	$52.08	$52.10	$52.10
Purchase #3	$130.35	8.849%	$141.8847	$141.88	$141.90	$141.90
Purchase #4	$36.78	12.258%	$41.2885	$41.29	$41.30	$41.30
Purchase #5	$134.61	9.170%	$146.9537	$146.95	$146.95	$147.00
Purchase #6	$50.48	6.753%	$53.8889	$53.89	$53.90	$53.90
Purchase #7	$127.33	10.128%	$140.226	$140.23	$140.25	$140.20
7 purchase totals =	$760.73		$817.3889	$817.38	$817.45	$817.50