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	$153.78	7.730%	$165.6672	$165.67	$165.65	$165.70
Purchase #2	$62.52	10.408%	$69.0271	$69.03	$69.05	$69.00
Purchase #3	$238.28	10.435%	$263.1445	$263.14	$263.15	$263.10
Purchase #4	$150.86	12.218%	$169.2921	$169.29	$169.30	$169.30
Purchase #5	$183.42	12.776%	$206.8537	$206.85	$206.85	$206.90
Purchase #6	$47.96	9.435%	$52.485	$52.49	$52.50	$52.50
Purchase #7	$73.88	5.696%	$78.0882	$78.09	$78.10	$78.10
7 purchase totals =	$910.70		$1,004.5578	$1,004.56	$1,004.60	$1,004.60