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	$171.88	3.823%	$178.451	$178.45	$178.45	$178.50
Purchase #2	$137.93	10.850%	$152.8954	$152.90	$152.90	$152.90
Purchase #3	$30.52	6.435%	$32.484	$32.48	$32.50	$32.50
Purchase #4	$225.36	7.710%	$242.7353	$242.74	$242.75	$242.70
Purchase #5	$47.48	11.700%	$53.0352	$53.04	$53.05	$53.00
Purchase #6	$247.98	6.769%	$264.7658	$264.77	$264.75	$264.80
Purchase #7	$213.97	4.866%	$224.3818	$224.38	$224.40	$224.40
7 purchase totals =	$1,075.12		$1,148.7485	$1,148.76	$1,148.80	$1,148.80