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	$163.32	5.775%	$172.7517	$172.75	$172.75	$172.80
Purchase #2	$142.89	5.816%	$151.2005	$151.20	$151.20	$151.20
Purchase #3	$93.73	7.532%	$100.7897	$100.79	$100.80	$100.80
Purchase #4	$141.36	6.854%	$151.0488	$151.05	$151.05	$151.00
Purchase #5	$159.36	3.138%	$164.3607	$164.36	$164.35	$164.40
Purchase #6	$30.82	5.865%	$32.6276	$32.63	$32.65	$32.60
Purchase #7	$65.63	9.740%	$72.0224	$72.02	$72.00	$72.00
7 purchase totals =	$797.11		$844.8014	$844.80	$844.80	$844.80