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	$159.30	3.191%	$164.3833	$164.38	$164.40	$164.40
Purchase #2	$242.68	7.590%	$261.0994	$261.10	$261.10	$261.10
Purchase #3	$109.56	4.723%	$114.7345	$114.73	$114.75	$114.70
Purchase #4	$243.69	10.476%	$269.219	$269.22	$269.20	$269.20
Purchase #5	$203.52	9.479%	$222.8117	$222.81	$222.80	$222.80
Purchase #6	$67.74	13.349%	$76.7826	$76.78	$76.80	$76.80
Purchase #7	$40.61	4.395%	$42.3948	$42.39	$42.40	$42.40
7 purchase totals =	$1,067.10		$1,151.4253	$1,151.41	$1,151.45	$1,151.40