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	$176.91	13.249%	$200.3488	$200.35	$200.35	$200.30
Purchase #2	$49.39	5.568%	$52.14	$52.14	$52.15	$52.10
Purchase #3	$29.25	4.829%	$30.6625	$30.66	$30.65	$30.70
Purchase #4	$108.73	13.359%	$123.2552	$123.26	$123.25	$123.30
Purchase #5	$176.51	4.249%	$184.0099	$184.01	$184.00	$184.00
Purchase #6	$221.36	7.780%	$238.5818	$238.58	$238.60	$238.60
Purchase #7	$76.39	7.492%	$82.1131	$82.11	$82.10	$82.10
7 purchase totals =	$838.54		$911.1113	$911.11	$911.10	$911.10