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	$211.88	12.766%	$238.9286	$238.93	$238.95	$238.90
Purchase #2	$17.59	3.523%	$18.2097	$18.21	$18.20	$18.20
Purchase #3	$92.37	3.565%	$95.663	$95.66	$95.65	$95.70
Purchase #4	$80.80	10.868%	$89.5813	$89.58	$89.60	$89.60
Purchase #5	$51.73	10.764%	$57.2982	$57.30	$57.30	$57.30
Purchase #6	$101.34	7.118%	$108.5534	$108.55	$108.55	$108.60
Purchase #7	$84.89	8.825%	$92.3815	$92.38	$92.40	$92.40
7 purchase totals =	$640.60		$700.6157	$700.61	$700.65	$700.70