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	$189.48	10.286%	$208.9699	$208.97	$208.95	$209.00
Purchase #2	$78.59	11.406%	$87.554	$87.55	$87.55	$87.60
Purchase #3	$239.35	7.298%	$256.8178	$256.82	$256.80	$256.80
Purchase #4	$89.40	10.151%	$98.475	$98.48	$98.50	$98.50
Purchase #5	$204.35	7.130%	$218.9202	$218.92	$218.90	$218.90
Purchase #6	$233.62	13.329%	$264.7592	$264.76	$264.75	$264.80
Purchase #7	$80.73	11.352%	$89.8945	$89.89	$89.90	$89.90
7 purchase totals =	$1,115.52		$1,225.3906	$1,225.39	$1,225.35	$1,225.50