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	$47.43	11.507%	$52.8878	$52.89	$52.90	$52.90
Purchase #2	$86.52	8.185%	$93.6017	$93.60	$93.60	$93.60
Purchase #3	$200.32	11.498%	$223.3528	$223.35	$223.35	$223.40
Purchase #4	$36.94	13.655%	$41.9842	$41.98	$42.00	$42.00
Purchase #5	$57.34	13.489%	$65.0746	$65.07	$65.05	$65.10
Purchase #6	$225.60	8.547%	$244.882	$244.88	$244.90	$244.90
Purchase #7	$62.80	13.499%	$71.2774	$71.28	$71.30	$71.30
7 purchase totals =	$716.95		$793.0605	$793.05	$793.10	$793.20