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	$110.42	7.797%	$119.0294	$119.03	$119.05	$119.00
Purchase #2	$147.53	6.323%	$156.8583	$156.86	$156.85	$156.90
Purchase #3	$225.84	13.862%	$257.1459	$257.15	$257.15	$257.10
Purchase #4	$57.48	3.873%	$59.7062	$59.71	$59.70	$59.70
Purchase #5	$139.56	11.693%	$155.8788	$155.88	$155.90	$155.90
Purchase #6	$67.89	6.647%	$72.4026	$72.40	$72.40	$72.40
Purchase #7	$127.64	5.647%	$134.8478	$134.85	$134.85	$134.80
7 purchase totals =	$876.36		$955.8690	$955.88	$955.90	$955.80