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	$140.50	5.871%	$148.7488	$148.75	$148.75	$148.70
Purchase #2	$106.41	9.825%	$116.8648	$116.86	$116.85	$116.90
Purchase #3	$66.90	7.840%	$72.145	$72.15	$72.15	$72.10
Purchase #4	$144.30	7.645%	$155.3317	$155.33	$155.35	$155.30
Purchase #5	$108.38	6.557%	$115.4865	$115.49	$115.50	$115.50
Purchase #6	$57.48	11.440%	$64.0557	$64.06	$64.05	$64.10
Purchase #7	$87.84	13.227%	$99.4586	$99.46	$99.45	$99.50
7 purchase totals =	$711.81		$772.0911	$772.10	$772.10	$772.10