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	$212.28	4.604%	$222.0534	$222.05	$222.05	$222.10
Purchase #2	$222.80	10.851%	$246.976	$246.98	$247.00	$247.00
Purchase #3	$89.97	7.237%	$96.4811	$96.48	$96.50	$96.50
Purchase #4	$81.86	4.300%	$85.38	$85.38	$85.40	$85.40
Purchase #5	$107.98	4.493%	$112.8315	$112.83	$112.85	$112.80
Purchase #6	$50.92	12.695%	$57.3843	$57.38	$57.40	$57.40
Purchase #7	$96.38	10.371%	$106.3756	$106.38	$106.40	$106.40
7 purchase totals =	$862.19		$927.4819	$927.48	$927.60	$927.60