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	$230.74	10.390%	$254.7139	$254.71	$254.70	$254.70
Purchase #2	$171.54	7.711%	$184.7674	$184.77	$184.75	$184.80
Purchase #3	$33.44	13.266%	$37.8762	$37.88	$37.90	$37.90
Purchase #4	$49.34	12.430%	$55.473	$55.47	$55.45	$55.50
Purchase #5	$209.95	6.606%	$223.8193	$223.82	$223.80	$223.80
Purchase #6	$222.93	11.367%	$248.2705	$248.27	$248.25	$248.30
Purchase #7	$86.31	3.678%	$89.4845	$89.48	$89.50	$89.50
7 purchase totals =	$1,004.25		$1,094.4048	$1,094.40	$1,094.35	$1,094.50