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	$202.39	10.130%	$222.8921	$222.89	$222.90	$222.90
Purchase #2	$32.88	7.160%	$35.2342	$35.23	$35.25	$35.20
Purchase #3	$198.49	10.774%	$219.8753	$219.88	$219.90	$219.90
Purchase #4	$73.78	4.130%	$76.8271	$76.83	$76.85	$76.80
Purchase #5	$177.46	8.676%	$192.8564	$192.86	$192.85	$192.90
Purchase #6	$65.69	8.221%	$71.0904	$71.09	$71.10	$71.10
Purchase #7	$42.50	11.238%	$47.2762	$47.28	$47.30	$47.30
7 purchase totals =	$793.19		$866.0517	$866.06	$866.15	$866.10