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	$48.89	6.291%	$51.9657	$51.97	$51.95	$52.00
Purchase #2	$160.91	4.710%	$168.4889	$168.49	$168.50	$168.50
Purchase #3	$194.60	11.440%	$216.8622	$216.86	$216.85	$216.90
Purchase #4	$222.75	5.614%	$235.2552	$235.26	$235.25	$235.30
Purchase #5	$247.40	11.173%	$275.042	$275.04	$275.05	$275.00
Purchase #6	$95.69	5.479%	$100.9329	$100.93	$100.95	$100.90
Purchase #7	$245.77	8.168%	$265.8445	$265.84	$265.85	$265.80
7 purchase totals =	$1,216.01		$1,314.3914	$1,314.39	$1,314.40	$1,314.40