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	$75.70	9.852%	$83.158	$83.16	$83.15	$83.20
Purchase #2	$110.76	7.697%	$119.2852	$119.29	$119.30	$119.30
Purchase #3	$38.70	9.266%	$42.2859	$42.29	$42.30	$42.30
Purchase #4	$219.41	9.444%	$240.1311	$240.13	$240.15	$240.10
Purchase #5	$229.40	12.391%	$257.825	$257.83	$257.85	$257.80
Purchase #6	$213.40	6.716%	$227.7319	$227.73	$227.75	$227.70
Purchase #7	$125.27	12.835%	$141.3484	$141.35	$141.35	$141.30
7 purchase totals =	$1,012.64		$1,111.7655	$1,111.78	$1,111.85	$1,111.70