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	$245.51	9.690%	$269.2999	$269.30	$269.30	$269.30
Purchase #2	$136.58	8.398%	$148.05	$148.05	$148.05	$148.10
Purchase #3	$120.97	4.378%	$126.2661	$126.27	$126.25	$126.30
Purchase #4	$180.83	5.808%	$191.3326	$191.33	$191.35	$191.30
Purchase #5	$38.89	4.445%	$40.6187	$40.62	$40.60	$40.60
Purchase #6	$173.27	9.325%	$189.4274	$189.43	$189.45	$189.40
Purchase #7	$44.97	3.534%	$46.5592	$46.56	$46.55	$46.60
7 purchase totals =	$941.02		$1,011.5539	$1,011.56	$1,011.55	$1,011.60