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	$215.41	3.499%	$222.9472	$222.95	$222.95	$222.90
Purchase #2	$215.85	11.562%	$240.8066	$240.81	$240.80	$240.80
Purchase #3	$133.92	4.441%	$139.8674	$139.87	$139.85	$139.90
Purchase #4	$94.53	9.159%	$103.188	$103.19	$103.20	$103.20
Purchase #5	$184.25	12.116%	$206.5737	$206.57	$206.55	$206.60
Purchase #6	$63.99	10.267%	$70.5599	$70.56	$70.55	$70.60
Purchase #7	$16.59	9.819%	$18.219	$18.22	$18.20	$18.20
7 purchase totals =	$924.54		$1,002.1618	$1,002.17	$1,002.10	$1,002.20