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	$151.59	3.204%	$156.4469	$156.45	$156.45	$156.40
Purchase #2	$219.94	8.231%	$238.0433	$238.04	$238.05	$238.00
Purchase #3	$24.71	4.652%	$25.8595	$25.86	$25.85	$25.90
Purchase #4	$238.87	9.162%	$260.7553	$260.76	$260.75	$260.80
Purchase #5	$162.75	3.629%	$168.6562	$168.66	$168.65	$168.70
Purchase #6	$223.81	9.379%	$244.8011	$244.80	$244.80	$244.80
Purchase #7	$188.95	9.192%	$206.3183	$206.32	$206.30	$206.30
7 purchase totals =	$1,210.62		$1,300.8806	$1,300.89	$1,300.85	$1,300.90