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	$151.26	3.799%	$157.0064	$157.01	$157.00	$157.00
Purchase #2	$250.52	10.671%	$277.253	$277.25	$277.25	$277.30
Purchase #3	$132.51	7.361%	$142.2641	$142.26	$142.25	$142.30
Purchase #4	$243.95	10.672%	$269.9843	$269.98	$270.00	$270.00
Purchase #5	$167.52	13.743%	$190.5423	$190.54	$190.55	$190.50
Purchase #6	$59.64	10.397%	$65.8408	$65.84	$65.85	$65.80
Purchase #7	$86.72	10.379%	$95.7207	$95.72	$95.70	$95.70
7 purchase totals =	$1,092.12		$1,198.6116	$1,198.60	$1,198.60	$1,198.60