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	$38.70	6.871%	$41.3591	$41.36	$41.35	$41.40
Purchase #2	$104.64	10.360%	$115.4807	$115.48	$115.50	$115.50
Purchase #3	$209.66	6.605%	$223.508	$223.51	$223.50	$223.50
Purchase #4	$139.60	3.257%	$144.1468	$144.15	$144.15	$144.10
Purchase #5	$213.62	4.421%	$223.0641	$223.06	$223.05	$223.10
Purchase #6	$169.40	11.424%	$188.7523	$188.75	$188.75	$188.80
Purchase #7	$198.57	13.771%	$225.9151	$225.92	$225.90	$225.90
7 purchase totals =	$1,074.19		$1,162.2261	$1,162.23	$1,162.20	$1,162.30