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	$64.29	12.240%	$72.1591	$72.16	$72.15	$72.20
Purchase #2	$175.51	3.717%	$182.0337	$182.03	$182.05	$182.00
Purchase #3	$31.35	6.122%	$33.2692	$33.27	$33.25	$33.30
Purchase #4	$121.69	13.181%	$137.73	$137.73	$137.75	$137.70
Purchase #5	$52.61	12.419%	$59.1436	$59.14	$59.15	$59.10
Purchase #6	$96.93	3.305%	$100.1335	$100.13	$100.15	$100.10
Purchase #7	$173.41	4.366%	$180.9811	$180.98	$181.00	$181.00
7 purchase totals =	$715.79		$765.4502	$765.44	$765.50	$765.40