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	$169.56	8.574%	$184.0981	$184.10	$184.10	$184.10
Purchase #2	$100.98	11.161%	$112.2504	$112.25	$112.25	$112.30
Purchase #3	$146.81	13.361%	$166.4253	$166.43	$166.45	$166.40
Purchase #4	$99.75	8.230%	$107.9594	$107.96	$107.95	$108.00
Purchase #5	$161.69	4.455%	$168.8933	$168.89	$168.90	$168.90
Purchase #6	$238.88	5.270%	$251.469	$251.47	$251.45	$251.50
Purchase #7	$117.50	8.388%	$127.3559	$127.36	$127.35	$127.40
7 purchase totals =	$1,035.17		$1,118.4514	$1,118.46	$1,118.45	$1,118.60