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	$69.44	13.550%	$78.8491	$78.85	$78.85	$78.80
Purchase #2	$57.48	13.114%	$65.0179	$65.02	$65.00	$65.00
Purchase #3	$198.54	6.718%	$211.8779	$211.88	$211.90	$211.90
Purchase #4	$24.34	6.322%	$25.8788	$25.88	$25.90	$25.90
Purchase #5	$160.64	4.210%	$167.4029	$167.40	$167.40	$167.40
Purchase #6	$89.67	11.813%	$100.2627	$100.26	$100.25	$100.30
Purchase #7	$181.34	10.437%	$200.2665	$200.27	$200.25	$200.30
7 purchase totals =	$781.45		$849.5558	$849.56	$849.55	$849.60