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	$185.34	5.849%	$196.1805	$196.18	$196.20	$196.20
Purchase #2	$236.77	5.805%	$250.5145	$250.51	$250.50	$250.50
Purchase #3	$210.92	7.213%	$226.1337	$226.13	$226.15	$226.10
Purchase #4	$131.69	10.303%	$145.258	$145.26	$145.25	$145.30
Purchase #5	$216.96	10.367%	$239.4522	$239.45	$239.45	$239.50
Purchase #6	$119.75	8.682%	$130.1467	$130.15	$130.15	$130.10
Purchase #7	$78.89	13.222%	$89.3208	$89.32	$89.30	$89.30
7 purchase totals =	$1,180.32		$1,277.0064	$1,277.00	$1,277.00	$1,277.00