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	$97.69	10.742%	$108.1839	$108.18	$108.20	$108.20
Purchase #2	$12.28	10.790%	$13.605	$13.61	$13.60	$13.60
Purchase #3	$226.30	9.834%	$248.5543	$248.55	$248.55	$248.60
Purchase #4	$216.41	12.458%	$243.3704	$243.37	$243.35	$243.40
Purchase #5	$72.50	5.435%	$76.4404	$76.44	$76.45	$76.40
Purchase #6	$54.76	7.772%	$59.0159	$59.02	$59.00	$59.00
Purchase #7	$142.77	6.202%	$151.6246	$151.62	$151.60	$151.60
7 purchase totals =	$822.71		$900.7945	$900.79	$900.75	$900.80