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	$63.39	3.434%	$65.5668	$65.57	$65.55	$65.60
Purchase #2	$86.82	8.567%	$94.2579	$94.26	$94.25	$94.30
Purchase #3	$86.49	10.359%	$95.4495	$95.45	$95.45	$95.40
Purchase #4	$91.59	6.605%	$97.6395	$97.64	$97.65	$97.60
Purchase #5	$217.85	10.809%	$241.3974	$241.40	$241.40	$241.40
Purchase #6	$83.69	6.396%	$89.0428	$89.04	$89.05	$89.00
Purchase #7	$90.95	9.282%	$99.392	$99.39	$99.40	$99.40
7 purchase totals =	$720.78		$782.7459	$782.75	$782.75	$782.70