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	$192.46	9.831%	$211.3807	$211.38	$211.40	$211.40
Purchase #2	$227.44	12.143%	$255.058	$255.06	$255.05	$255.10
Purchase #3	$137.47	6.107%	$145.8653	$145.87	$145.85	$145.90
Purchase #4	$37.56	4.797%	$39.3618	$39.36	$39.35	$39.40
Purchase #5	$53.47	8.222%	$57.8663	$57.87	$57.85	$57.90
Purchase #6	$156.46	7.175%	$167.686	$167.69	$167.70	$167.70
Purchase #7	$189.64	13.257%	$214.7806	$214.78	$214.80	$214.80
7 purchase totals =	$994.50		$1,091.9987	$1,092.01	$1,092.00	$1,092.20