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	$197.55	12.729%	$222.6961	$222.70	$222.70	$222.70
Purchase #2	$40.92	3.637%	$42.4083	$42.41	$42.40	$42.40
Purchase #3	$127.49	13.751%	$145.0211	$145.02	$145.00	$145.00
Purchase #4	$88.48	5.791%	$93.6039	$93.60	$93.60	$93.60
Purchase #5	$202.36	3.746%	$209.9404	$209.94	$209.95	$209.90
Purchase #6	$239.82	9.483%	$262.5621	$262.56	$262.55	$262.60
Purchase #7	$78.88	8.155%	$85.3127	$85.31	$85.30	$85.30
7 purchase totals =	$975.50		$1,061.5446	$1,061.54	$1,061.50	$1,061.50