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	$212.56	5.313%	$223.8533	$223.85	$223.85	$223.90
Purchase #2	$142.78	6.392%	$151.9065	$151.91	$151.90	$151.90
Purchase #3	$217.90	7.470%	$234.1771	$234.18	$234.20	$234.20
Purchase #4	$44.32	4.397%	$46.2688	$46.27	$46.25	$46.30
Purchase #5	$198.60	8.316%	$215.1156	$215.12	$215.10	$215.10
Purchase #6	$141.85	10.834%	$157.218	$157.22	$157.20	$157.20
Purchase #7	$96.65	7.185%	$103.5943	$103.59	$103.60	$103.60
7 purchase totals =	$1,054.66		$1,132.1336	$1,132.14	$1,132.10	$1,132.20