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	$79.60	11.861%	$89.0414	$89.04	$89.05	$89.00
Purchase #2	$232.52	4.725%	$243.5066	$243.51	$243.50	$243.50
Purchase #3	$9.52	7.277%	$10.2128	$10.21	$10.20	$10.20
Purchase #4	$84.90	7.227%	$91.0357	$91.04	$91.05	$91.00
Purchase #5	$96.79	13.390%	$109.7502	$109.75	$109.75	$109.80
Purchase #6	$52.25	6.248%	$55.5146	$55.51	$55.50	$55.50
Purchase #7	$136.71	8.657%	$148.545	$148.55	$148.55	$148.50
7 purchase totals =	$692.29		$747.6063	$747.61	$747.60	$747.50