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	$161.31	8.717%	$175.3714	$175.37	$175.35	$175.40
Purchase #2	$98.47	13.589%	$111.8511	$111.85	$111.85	$111.90
Purchase #3	$232.83	6.505%	$247.9756	$247.98	$248.00	$248.00
Purchase #4	$21.74	8.526%	$23.5936	$23.59	$23.60	$23.60
Purchase #5	$36.36	8.296%	$39.3764	$39.38	$39.40	$39.40
Purchase #6	$210.61	13.293%	$238.6064	$238.61	$238.60	$238.60
Purchase #7	$34.57	8.648%	$37.5596	$37.56	$37.55	$37.60
7 purchase totals =	$795.89		$874.3341	$874.34	$874.35	$874.50