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	$55.85	9.749%	$61.2948	$61.29	$61.30	$61.30
Purchase #2	$53.58	11.357%	$59.6651	$59.67	$59.65	$59.70
Purchase #3	$180.48	13.172%	$204.2528	$204.25	$204.25	$204.30
Purchase #4	$48.59	9.397%	$53.156	$53.16	$53.15	$53.20
Purchase #5	$58.75	7.250%	$63.0094	$63.01	$63.00	$63.00
Purchase #6	$224.78	7.536%	$241.7194	$241.72	$241.70	$241.70
Purchase #7	$96.61	13.771%	$109.9142	$109.91	$109.90	$109.90
7 purchase totals =	$718.64		$793.0117	$793.01	$792.95	$793.10