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	$214.76	10.427%	$237.153	$237.15	$237.15	$237.20
Purchase #2	$46.78	10.191%	$51.5473	$51.55	$51.55	$51.50
Purchase #3	$73.91	11.375%	$82.3173	$82.32	$82.30	$82.30
Purchase #4	$114.38	12.175%	$128.3058	$128.31	$128.30	$128.30
Purchase #5	$19.57	7.461%	$21.0301	$21.03	$21.05	$21.00
Purchase #6	$104.89	7.637%	$112.9004	$112.90	$112.90	$112.90
Purchase #7	$37.28	8.210%	$40.3407	$40.34	$40.35	$40.30
7 purchase totals =	$611.57		$673.5946	$673.60	$673.60	$673.50