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	$96.84	4.196%	$100.9034	$100.90	$100.90	$100.90
Purchase #2	$9.78	9.764%	$10.7349	$10.73	$10.75	$10.70
Purchase #3	$105.58	3.824%	$109.6174	$109.62	$109.60	$109.60
Purchase #4	$98.34	11.155%	$109.3098	$109.31	$109.30	$109.30
Purchase #5	$15.43	9.179%	$16.8463	$16.85	$16.85	$16.80
Purchase #6	$83.78	4.516%	$87.5635	$87.56	$87.55	$87.60
Purchase #7	$38.29	11.326%	$42.6267	$42.63	$42.65	$42.60
7 purchase totals =	$448.04		$477.6020	$477.60	$477.60	$477.50