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	$115.41	11.478%	$128.6568	$128.66	$128.65	$128.70
Purchase #2	$89.69	13.299%	$101.6179	$101.62	$101.60	$101.60
Purchase #3	$114.98	3.132%	$118.5812	$118.58	$118.60	$118.60
Purchase #4	$198.72	11.527%	$221.6265	$221.63	$221.65	$221.60
Purchase #5	$97.48	8.309%	$105.5796	$105.58	$105.60	$105.60
Purchase #6	$205.44	3.573%	$212.7804	$212.78	$212.80	$212.80
Purchase #7	$184.87	13.402%	$209.6463	$209.65	$209.65	$209.60
7 purchase totals =	$1,006.59		$1,098.4887	$1,098.50	$1,098.55	$1,098.50