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	$10.70	5.788%	$11.3193	$11.32	$11.30	$11.30
Purchase #2	$6.99	7.345%	$7.5034	$7.50	$7.50	$7.50
Purchase #3	$52.89	7.320%	$56.7615	$56.76	$56.75	$56.80
Purchase #4	$244.62	11.435%	$272.5923	$272.59	$272.60	$272.60
Purchase #5	$106.54	12.295%	$119.6391	$119.64	$119.65	$119.60
Purchase #6	$88.71	4.436%	$92.6452	$92.65	$92.65	$92.60
Purchase #7	$96.65	13.130%	$109.3401	$109.34	$109.35	$109.30
7 purchase totals =	$607.10		$669.8009	$669.80	$669.80	$669.70