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	$84.28	3.605%	$87.3183	$87.32	$87.30	$87.30
Purchase #2	$248.25	13.564%	$281.9226	$281.92	$281.90	$281.90
Purchase #3	$33.56	5.793%	$35.5041	$35.50	$35.50	$35.50
Purchase #4	$57.55	3.647%	$59.6488	$59.65	$59.65	$59.60
Purchase #5	$245.90	3.759%	$255.1434	$255.14	$255.15	$255.10
Purchase #6	$91.63	13.745%	$104.2245	$104.22	$104.20	$104.20
Purchase #7	$137.92	7.582%	$148.3771	$148.38	$148.40	$148.40
7 purchase totals =	$899.09		$972.1388	$972.13	$972.10	$972.00