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	$57.52	7.600%	$61.8915	$61.89	$61.90	$61.90
Purchase #2	$9.90	12.405%	$11.1281	$11.13	$11.15	$11.10
Purchase #3	$79.56	12.634%	$89.6116	$89.61	$89.60	$89.60
Purchase #4	$210.72	13.606%	$239.3906	$239.39	$239.40	$239.40
Purchase #5	$203.42	7.638%	$218.9572	$218.96	$218.95	$219.00
Purchase #6	$231.39	8.409%	$250.8476	$250.85	$250.85	$250.80
Purchase #7	$163.28	7.528%	$175.5717	$175.57	$175.55	$175.60
7 purchase totals =	$955.79		$1,047.3983	$1,047.40	$1,047.40	$1,047.40