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	$90.67	4.374%	$94.6359	$94.64	$94.65	$94.60
Purchase #2	$37.89	8.837%	$41.2383	$41.24	$41.25	$41.20
Purchase #3	$194.92	13.312%	$220.8678	$220.87	$220.85	$220.90
Purchase #4	$51.67	8.276%	$55.9462	$55.95	$55.95	$55.90
Purchase #5	$90.32	7.333%	$96.9432	$96.94	$96.95	$96.90
Purchase #6	$139.87	6.449%	$148.8902	$148.89	$148.90	$148.90
Purchase #7	$78.89	5.805%	$83.4696	$83.47	$83.45	$83.50
7 purchase totals =	$684.23		$741.9912	$742.00	$742.00	$741.90