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	$103.72	13.191%	$117.4017	$117.40	$117.40	$117.40
Purchase #2	$37.78	12.844%	$42.6325	$42.63	$42.65	$42.60
Purchase #3	$27.61	6.229%	$29.3298	$29.33	$29.35	$29.30
Purchase #4	$82.53	3.744%	$85.6199	$85.62	$85.60	$85.60
Purchase #5	$241.41	8.555%	$262.0626	$262.06	$262.05	$262.10
Purchase #6	$148.77	7.740%	$160.2848	$160.28	$160.30	$160.30
Purchase #7	$228.79	13.125%	$258.8187	$258.82	$258.80	$258.80
7 purchase totals =	$870.61		$956.1500	$956.14	$956.15	$956.10