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	$234.55	6.745%	$250.3704	$250.37	$250.35	$250.40
Purchase #2	$59.85	12.108%	$67.0966	$67.10	$67.10	$67.10
Purchase #3	$36.83	12.395%	$41.3951	$41.40	$41.40	$41.40
Purchase #4	$146.54	4.181%	$152.6668	$152.67	$152.65	$152.70
Purchase #5	$160.66	6.260%	$170.7173	$170.72	$170.70	$170.70
Purchase #6	$43.59	5.635%	$46.0463	$46.05	$46.05	$46.00
Purchase #7	$189.54	3.467%	$196.1114	$196.11	$196.10	$196.10
7 purchase totals =	$871.56		$924.4039	$924.42	$924.35	$924.40