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	$38.43	12.342%	$43.173	$43.17	$43.15	$43.20
Purchase #2	$73.33	10.409%	$80.9629	$80.96	$80.95	$81.00
Purchase #3	$105.61	5.791%	$111.7259	$111.73	$111.75	$111.70
Purchase #4	$9.38	9.113%	$10.2348	$10.23	$10.25	$10.20
Purchase #5	$81.35	4.295%	$84.844	$84.84	$84.85	$84.80
Purchase #6	$72.93	10.358%	$80.4841	$80.48	$80.50	$80.50
Purchase #7	$33.61	4.793%	$35.2209	$35.22	$35.20	$35.20
7 purchase totals =	$414.64		$446.6456	$446.63	$446.65	$446.60