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	$196.86	11.807%	$220.1033	$220.10	$220.10	$220.10
Purchase #2	$135.97	13.361%	$154.137	$154.14	$154.15	$154.10
Purchase #3	$130.51	6.761%	$139.3338	$139.33	$139.35	$139.30
Purchase #4	$74.76	4.660%	$78.2438	$78.24	$78.25	$78.20
Purchase #5	$74.51	4.325%	$77.7326	$77.73	$77.75	$77.70
Purchase #6	$39.77	6.758%	$42.4577	$42.46	$42.45	$42.50
Purchase #7	$142.42	4.813%	$149.2747	$149.27	$149.25	$149.30
7 purchase totals =	$794.80		$861.2829	$861.27	$861.30	$861.20