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	$250.63	10.737%	$277.5401	$277.54	$277.55	$277.50
Purchase #2	$37.89	5.524%	$39.983	$39.98	$40.00	$40.00
Purchase #3	$176.30	11.642%	$196.8248	$196.82	$196.80	$196.80
Purchase #4	$76.60	13.444%	$86.8981	$86.90	$86.90	$86.90
Purchase #5	$144.90	11.472%	$161.5229	$161.52	$161.50	$161.50
Purchase #6	$146.71	10.583%	$162.2363	$162.24	$162.25	$162.20
Purchase #7	$228.67	6.126%	$242.6783	$242.68	$242.70	$242.70
7 purchase totals =	$1,061.70		$1,167.6835	$1,167.68	$1,167.70	$1,167.60