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	$160.89	13.461%	$182.5474	$182.55	$182.55	$182.50
Purchase #2	$235.27	13.569%	$267.1938	$267.19	$267.20	$267.20
Purchase #3	$41.83	11.760%	$46.7492	$46.75	$46.75	$46.70
Purchase #4	$82.31	4.412%	$85.9415	$85.94	$85.95	$85.90
Purchase #5	$11.33	4.296%	$11.8167	$11.82	$11.80	$11.80
Purchase #6	$92.88	13.827%	$105.7225	$105.72	$105.70	$105.70
Purchase #7	$165.66	11.711%	$185.0604	$185.06	$185.05	$185.10
7 purchase totals =	$790.17		$885.0315	$885.03	$885.00	$884.90