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	$98.27	11.442%	$109.5141	$109.51	$109.50	$109.50
Purchase #2	$10.49	3.606%	$10.8683	$10.87	$10.85	$10.90
Purchase #3	$70.46	13.391%	$79.8953	$79.90	$79.90	$79.90
Purchase #4	$35.91	9.807%	$39.4317	$39.43	$39.45	$39.40
Purchase #5	$25.44	5.118%	$26.742	$26.74	$26.75	$26.70
Purchase #6	$65.40	9.492%	$71.6078	$71.61	$71.60	$71.60
Purchase #7	$78.25	10.269%	$86.2855	$86.29	$86.30	$86.30
7 purchase totals =	$384.22		$424.3447	$424.35	$424.35	$424.30