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	$34.58	5.470%	$36.4715	$36.47	$36.45	$36.50
Purchase #2	$70.39	7.868%	$75.9283	$75.93	$75.95	$75.90
Purchase #3	$27.52	4.404%	$28.732	$28.73	$28.75	$28.70
Purchase #4	$80.85	7.112%	$86.6001	$86.60	$86.60	$86.60
Purchase #5	$44.43	11.385%	$49.4884	$49.49	$49.50	$49.50
Purchase #6	$233.32	4.540%	$243.9127	$243.91	$243.90	$243.90
Purchase #7	$105.60	5.643%	$111.559	$111.56	$111.55	$111.60
7 purchase totals =	$596.69		$632.6920	$632.69	$632.70	$632.70