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	$53.54	8.324%	$57.9967	$58.00	$58.00	$58.00
Purchase #2	$151.26	3.154%	$156.0307	$156.03	$156.05	$156.00
Purchase #3	$162.54	4.730%	$170.2281	$170.23	$170.25	$170.20
Purchase #4	$87.72	13.732%	$99.7657	$99.77	$99.75	$99.80
Purchase #5	$10.97	6.427%	$11.675	$11.68	$11.70	$11.70
Purchase #6	$80.55	11.587%	$89.8833	$89.88	$89.90	$89.90
Purchase #7	$119.56	3.670%	$123.9479	$123.95	$123.95	$123.90
7 purchase totals =	$666.14		$709.5274	$709.54	$709.60	$709.50