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	$155.90	4.537%	$162.9732	$162.97	$162.95	$163.00
Purchase #2	$70.31	4.417%	$73.4156	$73.42	$73.40	$73.40
Purchase #3	$168.31	3.298%	$173.8609	$173.86	$173.85	$173.90
Purchase #4	$106.55	13.206%	$120.621	$120.62	$120.60	$120.60
Purchase #5	$150.99	11.804%	$168.8129	$168.81	$168.80	$168.80
Purchase #6	$79.70	12.230%	$89.4473	$89.45	$89.45	$89.40
Purchase #7	$213.38	13.833%	$242.8969	$242.90	$242.90	$242.90
7 purchase totals =	$945.14		$1,032.0278	$1,032.03	$1,031.95	$1,032.00