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	$61.84	6.373%	$65.7811	$65.78	$65.80	$65.80
Purchase #2	$84.40	13.705%	$95.967	$95.97	$95.95	$96.00
Purchase #3	$101.47	7.873%	$109.4587	$109.46	$109.45	$109.50
Purchase #4	$63.65	9.282%	$69.558	$69.56	$69.55	$69.60
Purchase #5	$126.72	12.336%	$142.3522	$142.35	$142.35	$142.40
Purchase #6	$18.34	8.435%	$19.887	$19.89	$19.90	$19.90
Purchase #7	$78.67	5.539%	$83.0275	$83.03	$83.05	$83.00
7 purchase totals =	$535.09		$586.0315	$586.04	$586.05	$586.20