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	$210.86	3.668%	$218.5943	$218.59	$218.60	$218.60
Purchase #2	$187.72	4.868%	$196.8582	$196.86	$196.85	$196.90
Purchase #3	$57.89	8.471%	$62.7939	$62.79	$62.80	$62.80
Purchase #4	$46.80	10.266%	$51.6045	$51.60	$51.60	$51.60
Purchase #5	$155.34	5.685%	$164.1711	$164.17	$164.15	$164.20
Purchase #6	$69.99	8.353%	$75.8363	$75.84	$75.85	$75.80
Purchase #7	$144.56	7.644%	$155.6102	$155.61	$155.60	$155.60
7 purchase totals =	$873.16		$925.4685	$925.46	$925.45	$925.50