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	$202.36	10.260%	$223.1221	$223.12	$223.10	$223.10
Purchase #2	$140.51	7.376%	$150.874	$150.87	$150.85	$150.90
Purchase #3	$209.60	11.197%	$233.0689	$233.07	$233.05	$233.10
Purchase #4	$121.98	7.498%	$131.1261	$131.13	$131.15	$131.10
Purchase #5	$186.37	10.477%	$205.896	$205.90	$205.90	$205.90
Purchase #6	$25.97	3.381%	$26.848	$26.85	$26.85	$26.80
Purchase #7	$81.57	11.517%	$90.9644	$90.96	$90.95	$91.00
7 purchase totals =	$968.36		$1,061.8995	$1,061.90	$1,061.85	$1,061.90