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	$146.51	12.648%	$165.0406	$165.04	$165.05	$165.00
Purchase #2	$187.34	6.416%	$199.3597	$199.36	$199.35	$199.40
Purchase #3	$56.87	4.254%	$59.2892	$59.29	$59.30	$59.30
Purchase #4	$232.86	4.272%	$242.8078	$242.81	$242.80	$242.80
Purchase #5	$46.82	7.257%	$50.2177	$50.22	$50.20	$50.20
Purchase #6	$151.44	7.591%	$162.9358	$162.94	$162.95	$162.90
Purchase #7	$207.77	12.255%	$233.2322	$233.23	$233.25	$233.20
7 purchase totals =	$1,029.61		$1,112.8830	$1,112.89	$1,112.90	$1,112.80