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	$173.35	7.227%	$185.878	$185.88	$185.90	$185.90
Purchase #2	$239.62	7.749%	$258.1882	$258.19	$258.20	$258.20
Purchase #3	$90.39	10.467%	$99.8511	$99.85	$99.85	$99.90
Purchase #4	$146.85	9.116%	$160.2368	$160.24	$160.25	$160.20
Purchase #5	$225.36	8.535%	$244.5945	$244.59	$244.60	$244.60
Purchase #6	$156.82	7.324%	$168.3055	$168.31	$168.30	$168.30
Purchase #7	$249.64	10.538%	$275.9471	$275.95	$275.95	$275.90
7 purchase totals =	$1,282.03		$1,393.0012	$1,393.01	$1,393.05	$1,393.00