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	$224.66	7.321%	$241.1074	$241.11	$241.10	$241.10
Purchase #2	$118.27	4.116%	$123.138	$123.14	$123.15	$123.10
Purchase #3	$234.34	10.315%	$258.5122	$258.51	$258.50	$258.50
Purchase #4	$153.54	7.269%	$164.7008	$164.70	$164.70	$164.70
Purchase #5	$157.83	5.328%	$166.2392	$166.24	$166.25	$166.20
Purchase #6	$61.89	6.705%	$66.0397	$66.04	$66.05	$66.00
Purchase #7	$150.84	11.745%	$168.5562	$168.56	$168.55	$168.60
7 purchase totals =	$1,101.37		$1,188.2935	$1,188.30	$1,188.30	$1,188.20