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	$146.31	11.317%	$162.8679	$162.87	$162.85	$162.90
Purchase #2	$51.74	10.269%	$57.0532	$57.05	$57.05	$57.10
Purchase #3	$155.34	12.491%	$174.7435	$174.74	$174.75	$174.70
Purchase #4	$62.59	3.813%	$64.9766	$64.98	$65.00	$65.00
Purchase #5	$89.98	12.624%	$101.3391	$101.34	$101.35	$101.30
Purchase #6	$61.46	9.220%	$67.1266	$67.13	$67.15	$67.10
Purchase #7	$56.56	7.527%	$60.8173	$60.82	$60.80	$60.80
7 purchase totals =	$623.98		$688.9242	$688.93	$688.95	$688.90