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	$241.30	10.591%	$266.8561	$266.86	$266.85	$266.90
Purchase #2	$155.84	10.137%	$171.6375	$171.64	$171.65	$171.60
Purchase #3	$61.30	7.358%	$65.8105	$65.81	$65.80	$65.80
Purchase #4	$222.77	10.120%	$245.3143	$245.31	$245.30	$245.30
Purchase #5	$52.42	10.690%	$58.0237	$58.02	$58.00	$58.00
Purchase #6	$147.55	7.276%	$158.2857	$158.29	$158.30	$158.30
Purchase #7	$151.38	6.828%	$161.7162	$161.72	$161.70	$161.70
7 purchase totals =	$1,032.56		$1,127.6440	$1,127.65	$1,127.60	$1,127.60