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	$180.90	5.199%	$190.305	$190.31	$190.30	$190.30
Purchase #2	$185.67	5.452%	$195.7927	$195.79	$195.80	$195.80
Purchase #3	$77.55	7.467%	$83.3407	$83.34	$83.35	$83.30
Purchase #4	$78.96	11.264%	$87.8541	$87.85	$87.85	$87.90
Purchase #5	$239.44	7.857%	$258.2528	$258.25	$258.25	$258.30
Purchase #6	$78.82	9.803%	$86.5467	$86.55	$86.55	$86.50
Purchase #7	$169.89	11.777%	$189.8979	$189.90	$189.90	$189.90
7 purchase totals =	$1,011.23		$1,091.9899	$1,091.99	$1,092.00	$1,092.00