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	$179.82	7.723%	$193.7075	$193.71	$193.70	$193.70
Purchase #2	$170.37	7.475%	$183.1052	$183.11	$183.10	$183.10
Purchase #3	$196.43	11.644%	$219.3023	$219.30	$219.30	$219.30
Purchase #4	$92.29	9.340%	$100.9099	$100.91	$100.90	$100.90
Purchase #5	$223.87	9.412%	$244.9406	$244.94	$244.95	$244.90
Purchase #6	$100.95	11.554%	$112.6138	$112.61	$112.60	$112.60
Purchase #7	$174.61	12.402%	$196.2651	$196.27	$196.25	$196.30
7 purchase totals =	$1,138.34		$1,250.8444	$1,250.85	$1,250.80	$1,250.80