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	$218.30	8.761%	$237.4253	$237.43	$237.45	$237.40
Purchase #2	$221.96	10.167%	$244.5267	$244.53	$244.55	$244.50
Purchase #3	$96.89	7.277%	$103.9407	$103.94	$103.95	$103.90
Purchase #4	$34.68	12.641%	$39.0639	$39.06	$39.05	$39.10
Purchase #5	$172.87	13.361%	$195.9672	$195.97	$195.95	$196.00
Purchase #6	$155.59	6.262%	$165.333	$165.33	$165.35	$165.30
Purchase #7	$99.71	4.738%	$104.4343	$104.43	$104.45	$104.40
7 purchase totals =	$1,000.00		$1,090.6911	$1,090.69	$1,090.75	$1,090.60