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	$103.66	7.804%	$111.7496	$111.75	$111.75	$111.70
Purchase #2	$55.35	13.435%	$62.7863	$62.79	$62.80	$62.80
Purchase #3	$91.89	3.663%	$95.2559	$95.26	$95.25	$95.30
Purchase #4	$189.60	13.570%	$215.3287	$215.33	$215.35	$215.30
Purchase #5	$32.85	7.154%	$35.2001	$35.20	$35.20	$35.20
Purchase #6	$133.35	5.583%	$140.7949	$140.79	$140.80	$140.80
Purchase #7	$100.60	4.707%	$105.3352	$105.34	$105.35	$105.30
7 purchase totals =	$707.30		$766.4507	$766.46	$766.50	$766.40