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	$59.30	4.349%	$61.879	$61.88	$61.90	$61.90
Purchase #2	$87.53	13.411%	$99.2686	$99.27	$99.25	$99.30
Purchase #3	$65.88	9.264%	$71.9831	$71.98	$72.00	$72.00
Purchase #4	$119.47	7.150%	$128.0121	$128.01	$128.00	$128.00
Purchase #5	$77.61	5.720%	$82.0493	$82.05	$82.05	$82.00
Purchase #6	$169.49	9.129%	$184.9627	$184.96	$184.95	$185.00
Purchase #7	$144.63	5.565%	$152.6787	$152.68	$152.70	$152.70
7 purchase totals =	$723.91		$780.8335	$780.83	$780.85	$780.90