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	$154.57	11.200%	$171.8818	$171.88	$171.90	$171.90
Purchase #2	$121.83	10.539%	$134.6697	$134.67	$134.65	$134.70
Purchase #3	$104.39	6.393%	$111.0637	$111.06	$111.05	$111.10
Purchase #4	$140.53	6.356%	$149.4621	$149.46	$149.45	$149.50
Purchase #5	$138.71	5.187%	$145.9049	$145.90	$145.90	$145.90
Purchase #6	$155.86	13.446%	$176.8169	$176.82	$176.80	$176.80
Purchase #7	$196.65	8.563%	$213.4891	$213.49	$213.50	$213.50
7 purchase totals =	$1,012.54		$1,103.2882	$1,103.28	$1,103.25	$1,103.40