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	$94.92	11.860%	$106.1775	$106.18	$106.20	$106.20
Purchase #2	$212.31	3.556%	$219.8597	$219.86	$219.85	$219.90
Purchase #3	$94.62	6.404%	$100.6795	$100.68	$100.70	$100.70
Purchase #4	$238.31	6.114%	$252.8803	$252.88	$252.90	$252.90
Purchase #5	$64.93	4.496%	$67.8493	$67.85	$67.85	$67.80
Purchase #6	$197.97	10.115%	$217.9947	$217.99	$218.00	$218.00
Purchase #7	$90.90	10.746%	$100.6681	$100.67	$100.65	$100.70
7 purchase totals =	$993.96		$1,066.1091	$1,066.11	$1,066.15	$1,066.20