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	$142.40	6.258%	$151.3114	$151.31	$151.30	$151.30
Purchase #2	$186.50	5.168%	$196.1383	$196.14	$196.15	$196.10
Purchase #3	$53.35	10.393%	$58.8947	$58.89	$58.90	$58.90
Purchase #4	$197.66	7.244%	$211.9785	$211.98	$212.00	$212.00
Purchase #5	$22.31	6.813%	$23.83	$23.83	$23.85	$23.80
Purchase #6	$134.81	11.360%	$150.1244	$150.12	$150.10	$150.10
Purchase #7	$34.93	3.583%	$36.1815	$36.18	$36.20	$36.20
7 purchase totals =	$771.96		$828.4588	$828.45	$828.50	$828.40