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	$60.47	11.215%	$67.2517	$67.25	$67.25	$67.30
Purchase #2	$172.59	6.485%	$183.7825	$183.78	$183.80	$183.80
Purchase #3	$249.36	12.741%	$281.131	$281.13	$281.15	$281.10
Purchase #4	$34.87	10.351%	$38.4794	$38.48	$38.50	$38.50
Purchase #5	$191.33	6.807%	$204.3538	$204.35	$204.35	$204.40
Purchase #6	$19.83	4.137%	$20.6504	$20.65	$20.65	$20.70
Purchase #7	$55.77	11.666%	$62.2761	$62.28	$62.30	$62.30
7 purchase totals =	$784.22		$857.9249	$857.92	$858.00	$858.10