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	$235.33	11.450%	$262.2753	$262.28	$262.30	$262.30
Purchase #2	$122.54	13.695%	$139.3219	$139.32	$139.30	$139.30
Purchase #3	$37.84	7.694%	$40.7514	$40.75	$40.75	$40.80
Purchase #4	$78.34	13.763%	$89.1219	$89.12	$89.10	$89.10
Purchase #5	$206.26	6.419%	$219.4998	$219.50	$219.50	$219.50
Purchase #6	$106.63	7.313%	$114.4279	$114.43	$114.45	$114.40
Purchase #7	$159.42	13.714%	$181.2829	$181.28	$181.30	$181.30
7 purchase totals =	$946.36		$1,046.6811	$1,046.68	$1,046.70	$1,046.70