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	$40.64	10.374%	$44.856	$44.86	$44.85	$44.90
Purchase #2	$172.84	10.229%	$190.5198	$190.52	$190.50	$190.50
Purchase #3	$247.47	12.440%	$278.2553	$278.26	$278.25	$278.30
Purchase #4	$25.88	11.671%	$28.9005	$28.90	$28.90	$28.90
Purchase #5	$57.42	7.699%	$61.8408	$61.84	$61.85	$61.80
Purchase #6	$58.77	5.601%	$62.0617	$62.06	$62.05	$62.10
Purchase #7	$150.90	11.834%	$168.7575	$168.76	$168.75	$168.80
7 purchase totals =	$753.92		$835.1916	$835.20	$835.15	$835.30