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	$45.95	10.138%	$50.6084	$50.61	$50.60	$50.60
Purchase #2	$29.90	6.636%	$31.8842	$31.88	$31.90	$31.90
Purchase #3	$75.83	8.682%	$82.4136	$82.41	$82.40	$82.40
Purchase #4	$170.44	13.279%	$193.0727	$193.07	$193.05	$193.10
Purchase #5	$100.59	11.236%	$111.8923	$111.89	$111.90	$111.90
Purchase #6	$196.44	13.192%	$222.3544	$222.35	$222.35	$222.40
Purchase #7	$92.87	11.248%	$103.316	$103.32	$103.30	$103.30
7 purchase totals =	$712.02		$795.5416	$795.53	$795.50	$795.60