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	$134.28	10.679%	$148.6198	$148.62	$148.60	$148.60
Purchase #2	$181.50	13.336%	$205.7048	$205.70	$205.70	$205.70
Purchase #3	$162.92	12.415%	$183.1465	$183.15	$183.15	$183.10
Purchase #4	$33.31	12.514%	$37.4784	$37.48	$37.50	$37.50
Purchase #5	$81.35	11.742%	$90.9021	$90.90	$90.90	$90.90
Purchase #6	$229.58	12.279%	$257.7701	$257.77	$257.75	$257.80
Purchase #7	$108.74	10.130%	$119.7554	$119.76	$119.75	$119.80
7 purchase totals =	$931.68		$1,043.3771	$1,043.38	$1,043.35	$1,043.40