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	$186.41	6.298%	$198.1501	$198.15	$198.15	$198.20
Purchase #2	$86.91	4.542%	$90.8575	$90.86	$90.85	$90.90
Purchase #3	$18.58	5.267%	$19.5586	$19.56	$19.55	$19.60
Purchase #4	$75.83	7.496%	$81.5142	$81.51	$81.50	$81.50
Purchase #5	$206.28	10.532%	$228.0054	$228.01	$228.00	$228.00
Purchase #6	$55.64	8.580%	$60.4139	$60.41	$60.40	$60.40
Purchase #7	$160.31	3.840%	$166.4659	$166.47	$166.45	$166.50
7 purchase totals =	$789.96		$844.9656	$844.97	$844.90	$845.10