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	$56.82	8.856%	$61.852	$61.85	$61.85	$61.90
Purchase #2	$188.96	12.325%	$212.2493	$212.25	$212.25	$212.20
Purchase #3	$214.70	3.640%	$222.5151	$222.52	$222.50	$222.50
Purchase #4	$149.39	7.513%	$160.6137	$160.61	$160.60	$160.60
Purchase #5	$133.30	7.117%	$142.787	$142.79	$142.80	$142.80
Purchase #6	$130.33	8.424%	$141.309	$141.31	$141.30	$141.30
Purchase #7	$164.60	12.646%	$185.4153	$185.42	$185.40	$185.40
7 purchase totals =	$1,038.10		$1,126.7414	$1,126.75	$1,126.70	$1,126.70