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	$156.88	7.121%	$168.0514	$168.05	$168.05	$168.10
Purchase #2	$109.57	12.266%	$123.0099	$123.01	$123.00	$123.00
Purchase #3	$23.58	10.510%	$26.0583	$26.06	$26.05	$26.10
Purchase #4	$247.70	4.168%	$258.0241	$258.02	$258.00	$258.00
Purchase #5	$212.81	4.735%	$222.8866	$222.89	$222.90	$222.90
Purchase #6	$60.89	10.831%	$67.485	$67.49	$67.50	$67.50
Purchase #7	$152.57	6.290%	$162.1667	$162.17	$162.15	$162.20
7 purchase totals =	$964.00		$1,027.6820	$1,027.69	$1,027.65	$1,027.80