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	$9.61	12.740%	$10.8343	$10.83	$10.85	$10.80
Purchase #2	$41.49	6.236%	$44.0773	$44.08	$44.10	$44.10
Purchase #3	$205.25	5.254%	$216.0338	$216.03	$216.05	$216.00
Purchase #4	$71.59	12.505%	$80.5423	$80.54	$80.55	$80.50
Purchase #5	$80.96	11.219%	$90.0429	$90.04	$90.05	$90.00
Purchase #6	$168.74	7.286%	$181.0344	$181.03	$181.05	$181.00
Purchase #7	$97.76	3.808%	$101.4827	$101.48	$101.50	$101.50
7 purchase totals =	$675.40		$724.0477	$724.03	$724.15	$723.90