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	$95.52	4.422%	$99.7439	$99.74	$99.75	$99.70
Purchase #2	$231.62	7.425%	$248.8178	$248.82	$248.80	$248.80
Purchase #3	$39.80	13.645%	$45.2307	$45.23	$45.25	$45.20
Purchase #4	$170.90	5.260%	$179.8893	$179.89	$179.90	$179.90
Purchase #5	$161.42	4.687%	$168.9858	$168.99	$169.00	$169.00
Purchase #6	$71.40	13.851%	$81.2896	$81.29	$81.30	$81.30
Purchase #7	$200.30	6.163%	$212.6445	$212.64	$212.65	$212.60
7 purchase totals =	$970.96		$1,036.6016	$1,036.60	$1,036.65	$1,036.50