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	$201.59	6.843%	$215.3848	$215.38	$215.40	$215.40
Purchase #2	$53.31	10.664%	$58.995	$59.00	$59.00	$59.00
Purchase #3	$83.77	10.654%	$92.6949	$92.69	$92.70	$92.70
Purchase #4	$67.77	8.146%	$73.2905	$73.29	$73.30	$73.30
Purchase #5	$117.91	13.359%	$133.6616	$133.66	$133.65	$133.70
Purchase #6	$156.42	9.706%	$171.6021	$171.60	$171.60	$171.60
Purchase #7	$168.57	9.657%	$184.8488	$184.85	$184.85	$184.80
7 purchase totals =	$849.34		$930.4777	$930.47	$930.50	$930.50