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	$167.86	13.259%	$190.1166	$190.12	$190.10	$190.10
Purchase #2	$223.78	6.421%	$238.1489	$238.15	$238.15	$238.10
Purchase #3	$210.48	13.333%	$238.5433	$238.54	$238.55	$238.50
Purchase #4	$8.69	10.604%	$9.6115	$9.61	$9.60	$9.60
Purchase #5	$221.61	11.485%	$247.0619	$247.06	$247.05	$247.10
Purchase #6	$64.59	12.874%	$72.9053	$72.91	$72.90	$72.90
Purchase #7	$163.67	8.714%	$177.9322	$177.93	$177.95	$177.90
7 purchase totals =	$1,060.68		$1,174.3197	$1,174.32	$1,174.30	$1,174.20