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	$93.53	6.138%	$99.2709	$99.27	$99.25	$99.30
Purchase #2	$188.63	3.565%	$195.3547	$195.35	$195.35	$195.40
Purchase #3	$94.75	6.309%	$100.7278	$100.73	$100.75	$100.70
Purchase #4	$149.47	9.809%	$164.1315	$164.13	$164.15	$164.10
Purchase #5	$77.50	6.460%	$82.5065	$82.51	$82.50	$82.50
Purchase #6	$13.30	4.796%	$13.9379	$13.94	$13.95	$13.90
Purchase #7	$102.84	6.824%	$109.8578	$109.86	$109.85	$109.90
7 purchase totals =	$720.02		$765.7871	$765.79	$765.80	$765.80