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	$130.78	10.210%	$144.1326	$144.13	$144.15	$144.10
Purchase #2	$83.25	8.104%	$89.9966	$90.00	$90.00	$90.00
Purchase #3	$38.28	9.219%	$41.809	$41.81	$41.80	$41.80
Purchase #4	$195.33	6.424%	$207.878	$207.88	$207.90	$207.90
Purchase #5	$132.49	13.659%	$150.5868	$150.59	$150.60	$150.60
Purchase #6	$205.95	6.618%	$219.5798	$219.58	$219.60	$219.60
Purchase #7	$95.38	11.686%	$106.5261	$106.53	$106.55	$106.50
7 purchase totals =	$881.46		$960.5089	$960.52	$960.60	$960.50