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	$186.69	6.433%	$198.6998	$198.70	$198.70	$198.70
Purchase #2	$10.73	4.647%	$11.2286	$11.23	$11.25	$11.20
Purchase #3	$79.81	12.568%	$89.8405	$89.84	$89.85	$89.80
Purchase #4	$218.81	5.410%	$230.6476	$230.65	$230.65	$230.60
Purchase #5	$126.35	10.448%	$139.551	$139.55	$139.55	$139.60
Purchase #6	$74.75	13.735%	$85.0169	$85.02	$85.00	$85.00
Purchase #7	$124.79	5.157%	$131.2254	$131.23	$131.25	$131.20
7 purchase totals =	$821.93		$886.2098	$886.22	$886.25	$886.10