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	$133.63	7.451%	$143.5868	$143.59	$143.60	$143.60
Purchase #2	$241.31	11.433%	$268.899	$268.90	$268.90	$268.90
Purchase #3	$224.33	7.714%	$241.6348	$241.63	$241.65	$241.60
Purchase #4	$139.57	6.442%	$148.5611	$148.56	$148.55	$148.60
Purchase #5	$220.97	5.590%	$233.3222	$233.32	$233.30	$233.30
Purchase #6	$206.57	5.219%	$217.3509	$217.35	$217.35	$217.40
Purchase #7	$132.65	13.686%	$150.8045	$150.80	$150.80	$150.80
7 purchase totals =	$1,299.03		$1,404.1593	$1,404.15	$1,404.15	$1,404.20