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	$90.72	4.339%	$94.6563	$94.66	$94.65	$94.70
Purchase #2	$32.75	11.569%	$36.5388	$36.54	$36.55	$36.50
Purchase #3	$56.29	4.872%	$59.0324	$59.03	$59.05	$59.00
Purchase #4	$46.90	13.727%	$53.338	$53.34	$53.35	$53.30
Purchase #5	$218.30	11.533%	$243.4765	$243.48	$243.50	$243.50
Purchase #6	$173.48	3.317%	$179.2343	$179.23	$179.25	$179.20
Purchase #7	$19.60	9.113%	$21.3861	$21.39	$21.40	$21.40
7 purchase totals =	$638.04		$687.6624	$687.67	$687.75	$687.60