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	$37.86	10.287%	$41.7547	$41.75	$41.75	$41.80
Purchase #2	$151.44	11.411%	$168.7208	$168.72	$168.70	$168.70
Purchase #3	$29.46	13.380%	$33.4017	$33.40	$33.40	$33.40
Purchase #4	$78.47	7.713%	$84.5224	$84.52	$84.50	$84.50
Purchase #5	$67.83	5.861%	$71.8055	$71.81	$71.80	$71.80
Purchase #6	$158.55	5.254%	$166.8802	$166.88	$166.90	$166.90
Purchase #7	$175.68	10.405%	$193.9595	$193.96	$193.95	$194.00
7 purchase totals =	$699.29		$761.0448	$761.04	$761.00	$761.10