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	$231.63	5.349%	$244.0199	$244.02	$244.00	$244.00
Purchase #2	$160.54	13.153%	$181.6558	$181.66	$181.65	$181.70
Purchase #3	$140.89	12.511%	$158.5167	$158.52	$158.50	$158.50
Purchase #4	$152.96	12.389%	$171.9102	$171.91	$171.90	$171.90
Purchase #5	$76.58	4.325%	$79.8921	$79.89	$79.90	$79.90
Purchase #6	$149.94	4.306%	$156.3964	$156.40	$156.40	$156.40
Purchase #7	$81.75	11.845%	$91.4333	$91.43	$91.45	$91.40
7 purchase totals =	$994.29		$1,083.8244	$1,083.83	$1,083.80	$1,083.80