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	$64.43	12.452%	$72.4528	$72.45	$72.45	$72.50
Purchase #2	$211.90	5.480%	$223.5121	$223.51	$223.50	$223.50
Purchase #3	$230.89	7.684%	$248.6316	$248.63	$248.65	$248.60
Purchase #4	$27.61	3.222%	$28.4996	$28.50	$28.50	$28.50
Purchase #5	$160.31	12.182%	$179.839	$179.84	$179.85	$179.80
Purchase #6	$82.31	3.846%	$85.4756	$85.48	$85.50	$85.50
Purchase #7	$157.85	4.246%	$164.5523	$164.55	$164.55	$164.60
7 purchase totals =	$935.30		$1,002.9630	$1,002.96	$1,003.00	$1,003.00