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	$49.66	9.684%	$54.4691	$54.47	$54.45	$54.50
Purchase #2	$225.31	12.686%	$253.8928	$253.89	$253.90	$253.90
Purchase #3	$57.30	12.574%	$64.5049	$64.50	$64.50	$64.50
Purchase #4	$153.51	9.871%	$168.663	$168.66	$168.65	$168.70
Purchase #5	$24.66	7.157%	$26.4249	$26.42	$26.40	$26.40
Purchase #6	$163.42	11.862%	$182.8049	$182.80	$182.80	$182.80
Purchase #7	$173.56	10.352%	$191.5269	$191.53	$191.55	$191.50
7 purchase totals =	$847.42		$942.2865	$942.27	$942.25	$942.30