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	$12.91	11.513%	$14.3963	$14.40	$14.40	$14.40
Purchase #2	$155.59	11.177%	$172.9803	$172.98	$173.00	$173.00
Purchase #3	$151.36	11.528%	$168.8088	$168.81	$168.80	$168.80
Purchase #4	$201.96	4.312%	$210.6685	$210.67	$210.65	$210.70
Purchase #5	$159.33	12.676%	$179.5267	$179.53	$179.55	$179.50
Purchase #6	$120.41	8.307%	$130.4125	$130.41	$130.40	$130.40
Purchase #7	$118.26	7.830%	$127.5198	$127.52	$127.50	$127.50
7 purchase totals =	$919.82		$1,004.3129	$1,004.32	$1,004.30	$1,004.30