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	$23.71	8.130%	$25.6376	$25.64	$25.65	$25.60
Purchase #2	$225.37	6.555%	$240.143	$240.14	$240.15	$240.10
Purchase #3	$165.94	10.825%	$183.903	$183.90	$183.90	$183.90
Purchase #4	$90.76	11.168%	$100.8961	$100.90	$100.90	$100.90
Purchase #5	$214.29	12.156%	$240.3391	$240.34	$240.35	$240.30
Purchase #6	$85.36	10.481%	$94.3066	$94.31	$94.30	$94.30
Purchase #7	$136.51	12.478%	$153.5437	$153.54	$153.55	$153.50
7 purchase totals =	$941.94		$1,038.7691	$1,038.77	$1,038.80	$1,038.60