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	$184.60	13.511%	$209.5413	$209.54	$209.55	$209.50
Purchase #2	$205.66	11.499%	$229.3088	$229.31	$229.30	$229.30
Purchase #3	$247.98	10.211%	$273.3012	$273.30	$273.30	$273.30
Purchase #4	$202.31	5.396%	$213.2266	$213.23	$213.25	$213.20
Purchase #5	$189.53	12.443%	$213.1132	$213.11	$213.10	$213.10
Purchase #6	$193.29	6.208%	$205.2894	$205.29	$205.30	$205.30
Purchase #7	$140.54	11.221%	$156.31	$156.31	$156.30	$156.30
7 purchase totals =	$1,363.91		$1,500.0905	$1,500.09	$1,500.10	$1,500.00