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	$72.87	8.455%	$79.0312	$79.03	$79.05	$79.00
Purchase #2	$114.81	11.759%	$128.3105	$128.31	$128.30	$128.30
Purchase #3	$227.63	7.373%	$244.4132	$244.41	$244.40	$244.40
Purchase #4	$236.78	8.492%	$256.8874	$256.89	$256.90	$256.90
Purchase #5	$158.27	4.545%	$165.4634	$165.46	$165.45	$165.50
Purchase #6	$155.75	11.351%	$173.4292	$173.43	$173.45	$173.40
Purchase #7	$21.54	10.687%	$23.842	$23.84	$23.85	$23.80
7 purchase totals =	$987.65		$1,071.3769	$1,071.37	$1,071.40	$1,071.30