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	$110.28	9.307%	$120.5438	$120.54	$120.55	$120.50
Purchase #2	$125.72	11.225%	$139.8321	$139.83	$139.85	$139.80
Purchase #3	$20.56	5.199%	$21.6289	$21.63	$21.65	$21.60
Purchase #4	$167.94	7.122%	$179.9007	$179.90	$179.90	$179.90
Purchase #5	$213.60	13.588%	$242.624	$242.62	$242.60	$242.60
Purchase #6	$221.54	9.386%	$242.3337	$242.33	$242.35	$242.30
Purchase #7	$203.45	9.530%	$222.8388	$222.84	$222.85	$222.80
7 purchase totals =	$1,063.09		$1,169.7020	$1,169.69	$1,169.75	$1,169.50