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	$40.39	12.742%	$45.5365	$45.54	$45.55	$45.50
Purchase #2	$10.73	5.508%	$11.321	$11.32	$11.30	$11.30
Purchase #3	$198.47	6.538%	$211.446	$211.45	$211.45	$211.40
Purchase #4	$127.94	5.304%	$134.7259	$134.73	$134.75	$134.70
Purchase #5	$232.59	13.614%	$264.2548	$264.25	$264.25	$264.30
Purchase #6	$100.35	5.433%	$105.802	$105.80	$105.80	$105.80
Purchase #7	$213.64	9.576%	$234.0982	$234.10	$234.10	$234.10
7 purchase totals =	$924.11		$1,007.1844	$1,007.19	$1,007.20	$1,007.10