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	$62.46	9.395%	$68.3281	$68.33	$68.35	$68.30
Purchase #2	$12.34	12.431%	$13.874	$13.87	$13.85	$13.90
Purchase #3	$155.75	11.808%	$174.141	$174.14	$174.15	$174.10
Purchase #4	$220.43	11.631%	$246.0682	$246.07	$246.05	$246.10
Purchase #5	$231.49	3.210%	$238.9208	$238.92	$238.90	$238.90
Purchase #6	$124.42	5.606%	$131.395	$131.40	$131.40	$131.40
Purchase #7	$117.27	11.560%	$130.8264	$130.83	$130.85	$130.80
7 purchase totals =	$924.16		$1,003.5535	$1,003.56	$1,003.55	$1,003.50