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	$54.76	12.360%	$61.5283	$61.53	$61.55	$61.50
Purchase #2	$74.63	8.372%	$80.878	$80.88	$80.90	$80.90
Purchase #3	$45.41	7.863%	$48.9806	$48.98	$49.00	$49.00
Purchase #4	$13.63	8.752%	$14.8229	$14.82	$14.80	$14.80
Purchase #5	$142.85	8.731%	$155.3222	$155.32	$155.30	$155.30
Purchase #6	$172.69	10.742%	$191.2404	$191.24	$191.25	$191.20
Purchase #7	$49.34	13.740%	$56.1193	$56.12	$56.10	$56.10
7 purchase totals =	$553.31		$608.8917	$608.89	$608.90	$608.80