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	$28.74	8.773%	$31.2614	$31.26	$31.25	$31.30
Purchase #2	$68.54	6.831%	$73.222	$73.22	$73.20	$73.20
Purchase #3	$99.60	11.637%	$111.1905	$111.19	$111.20	$111.20
Purchase #4	$37.60	3.656%	$38.9747	$38.97	$38.95	$39.00
Purchase #5	$235.60	6.193%	$250.1907	$250.19	$250.20	$250.20
Purchase #6	$184.32	3.362%	$190.5168	$190.52	$190.50	$190.50
Purchase #7	$172.93	3.689%	$179.3094	$179.31	$179.30	$179.30
7 purchase totals =	$827.33		$874.6655	$874.66	$874.60	$874.70