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	$74.80	4.199%	$77.9409	$77.94	$77.95	$77.90
Purchase #2	$92.38	4.476%	$96.5149	$96.51	$96.50	$96.50
Purchase #3	$97.86	8.449%	$106.1282	$106.13	$106.15	$106.10
Purchase #4	$114.32	12.778%	$128.9278	$128.93	$128.95	$128.90
Purchase #5	$80.54	13.830%	$91.6787	$91.68	$91.70	$91.70
Purchase #6	$136.29	10.225%	$150.2257	$150.23	$150.25	$150.20
Purchase #7	$102.59	5.440%	$108.1709	$108.17	$108.15	$108.20
7 purchase totals =	$698.78		$759.5871	$759.59	$759.65	$759.50