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	$32.85	6.776%	$35.0759	$35.08	$35.10	$35.10
Purchase #2	$15.49	4.353%	$16.1643	$16.16	$16.15	$16.20
Purchase #3	$227.39	12.361%	$255.4977	$255.50	$255.50	$255.50
Purchase #4	$191.27	12.738%	$215.634	$215.63	$215.65	$215.60
Purchase #5	$82.76	7.619%	$89.0655	$89.07	$89.05	$89.10
Purchase #6	$231.56	5.856%	$245.1202	$245.12	$245.10	$245.10
Purchase #7	$216.62	9.483%	$237.1621	$237.16	$237.15	$237.20
7 purchase totals =	$997.94		$1,093.7197	$1,093.72	$1,093.70	$1,093.80