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	$175.53	9.549%	$192.2914	$192.29	$192.30	$192.30
Purchase #2	$164.26	7.104%	$175.929	$175.93	$175.95	$175.90
Purchase #3	$82.57	9.432%	$90.358	$90.36	$90.35	$90.40
Purchase #4	$240.82	8.223%	$260.6226	$260.62	$260.60	$260.60
Purchase #5	$198.27	4.328%	$206.8511	$206.85	$206.85	$206.90
Purchase #6	$36.32	4.282%	$37.8752	$37.88	$37.90	$37.90
Purchase #7	$91.64	8.260%	$99.2095	$99.21	$99.20	$99.20
7 purchase totals =	$989.41		$1,063.1368	$1,063.14	$1,063.15	$1,063.20