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	$100.83	8.319%	$109.218	$109.22	$109.20	$109.20
Purchase #2	$168.46	6.568%	$179.5245	$179.52	$179.50	$179.50
Purchase #3	$248.99	9.453%	$272.527	$272.53	$272.55	$272.50
Purchase #4	$83.64	6.777%	$89.3083	$89.31	$89.30	$89.30
Purchase #5	$115.73	8.182%	$125.199	$125.20	$125.20	$125.20
Purchase #6	$110.76	8.172%	$119.8113	$119.81	$119.80	$119.80
Purchase #7	$177.92	6.818%	$190.0506	$190.05	$190.05	$190.10
7 purchase totals =	$1,006.33		$1,085.6387	$1,085.64	$1,085.60	$1,085.60