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	$204.37	8.851%	$222.4588	$222.46	$222.45	$222.50
Purchase #2	$127.50	7.332%	$136.8483	$136.85	$136.85	$136.80
Purchase #3	$198.79	11.712%	$222.0723	$222.07	$222.05	$222.10
Purchase #4	$169.59	11.199%	$188.5824	$188.58	$188.60	$188.60
Purchase #5	$179.73	4.641%	$188.0713	$188.07	$188.05	$188.10
Purchase #6	$73.86	9.203%	$80.6573	$80.66	$80.65	$80.70
Purchase #7	$85.38	4.483%	$89.2076	$89.21	$89.20	$89.20
7 purchase totals =	$1,039.22		$1,127.8980	$1,127.90	$1,127.85	$1,128.00