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	$183.96	3.616%	$190.612	$190.61	$190.60	$190.60
Purchase #2	$88.29	9.795%	$96.938	$96.94	$96.95	$96.90
Purchase #3	$148.40	12.165%	$166.4529	$166.45	$166.45	$166.50
Purchase #4	$232.34	7.228%	$249.1335	$249.13	$249.15	$249.10
Purchase #5	$10.40	9.302%	$11.3674	$11.37	$11.35	$11.40
Purchase #6	$50.77	6.368%	$54.003	$54.00	$54.00	$54.00
Purchase #7	$101.94	6.763%	$108.8342	$108.83	$108.85	$108.80
7 purchase totals =	$816.10		$877.3410	$877.33	$877.35	$877.30