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	$219.96	10.274%	$242.5587	$242.56	$242.55	$242.60
Purchase #2	$182.57	7.279%	$195.8593	$195.86	$195.85	$195.90
Purchase #3	$82.89	11.562%	$92.4737	$92.47	$92.45	$92.50
Purchase #4	$236.80	13.232%	$268.1334	$268.13	$268.15	$268.10
Purchase #5	$100.34	4.225%	$104.5794	$104.58	$104.60	$104.60
Purchase #6	$31.62	6.133%	$33.5593	$33.56	$33.55	$33.60
Purchase #7	$163.36	3.178%	$168.5516	$168.55	$168.55	$168.60
7 purchase totals =	$1,017.54		$1,105.7154	$1,105.71	$1,105.70	$1,105.90