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	$165.77	3.427%	$171.4509	$171.45	$171.45	$171.50
Purchase #2	$159.81	4.598%	$167.1581	$167.16	$167.15	$167.20
Purchase #3	$74.46	12.534%	$83.7928	$83.79	$83.80	$83.80
Purchase #4	$209.43	11.358%	$233.2171	$233.22	$233.20	$233.20
Purchase #5	$221.28	7.844%	$238.6372	$238.64	$238.65	$238.60
Purchase #6	$149.67	5.768%	$158.303	$158.30	$158.30	$158.30
Purchase #7	$31.45	6.430%	$33.4722	$33.47	$33.45	$33.50
7 purchase totals =	$1,011.87		$1,086.0313	$1,086.03	$1,086.00	$1,086.10