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	$110.97	6.626%	$118.3229	$118.32	$118.30	$118.30
Purchase #2	$136.35	11.771%	$152.3998	$152.40	$152.40	$152.40
Purchase #3	$90.54	11.442%	$100.8996	$100.90	$100.90	$100.90
Purchase #4	$61.82	3.684%	$64.0974	$64.10	$64.10	$64.10
Purchase #5	$190.97	6.677%	$203.7211	$203.72	$203.70	$203.70
Purchase #6	$238.70	3.153%	$246.2262	$246.23	$246.25	$246.20
Purchase #7	$179.82	10.180%	$198.1257	$198.13	$198.15	$198.10
7 purchase totals =	$1,009.17		$1,083.7927	$1,083.80	$1,083.80	$1,083.70