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	$119.29	10.553%	$131.8787	$131.88	$131.90	$131.90
Purchase #2	$133.70	13.755%	$152.0904	$152.09	$152.10	$152.10
Purchase #3	$61.43	9.679%	$67.3758	$67.38	$67.40	$67.40
Purchase #4	$38.30	7.474%	$41.1625	$41.16	$41.15	$41.20
Purchase #5	$177.95	6.445%	$189.4189	$189.42	$189.40	$189.40
Purchase #6	$46.73	7.442%	$50.2076	$50.21	$50.20	$50.20
Purchase #7	$17.43	11.178%	$19.3783	$19.38	$19.40	$19.40
7 purchase totals =	$594.83		$651.5122	$651.52	$651.55	$651.60