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	$33.44	7.502%	$35.9487	$35.95	$35.95	$35.90
Purchase #2	$82.78	9.625%	$90.7476	$90.75	$90.75	$90.70
Purchase #3	$129.32	13.392%	$146.6385	$146.64	$146.65	$146.60
Purchase #4	$175.63	10.173%	$193.4968	$193.50	$193.50	$193.50
Purchase #5	$115.90	7.331%	$124.3966	$124.40	$124.40	$124.40
Purchase #6	$190.88	4.521%	$199.5097	$199.51	$199.50	$199.50
Purchase #7	$129.40	10.139%	$142.5199	$142.52	$142.50	$142.50
7 purchase totals =	$857.35		$933.2578	$933.27	$933.25	$933.10