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	$126.77	3.156%	$130.7709	$130.77	$130.75	$130.80
Purchase #2	$80.27	13.317%	$90.9596	$90.96	$90.95	$91.00
Purchase #3	$221.59	11.476%	$247.0197	$247.02	$247.00	$247.00
Purchase #4	$234.89	6.355%	$249.8173	$249.82	$249.80	$249.80
Purchase #5	$112.49	4.525%	$117.5802	$117.58	$117.60	$117.60
Purchase #6	$175.86	3.140%	$181.382	$181.38	$181.40	$181.40
Purchase #7	$176.60	13.555%	$200.5381	$200.54	$200.55	$200.50
7 purchase totals =	$1,128.47		$1,218.0678	$1,218.07	$1,218.05	$1,218.10