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	$86.67	8.854%	$94.3438	$94.34	$94.35	$94.30
Purchase #2	$99.62	10.401%	$109.9815	$109.98	$110.00	$110.00
Purchase #3	$179.95	10.728%	$199.255	$199.26	$199.25	$199.30
Purchase #4	$53.85	10.212%	$59.3492	$59.35	$59.35	$59.30
Purchase #5	$30.60	5.446%	$32.2665	$32.27	$32.25	$32.30
Purchase #6	$27.56	10.535%	$30.4634	$30.46	$30.45	$30.50
Purchase #7	$57.59	4.865%	$60.3918	$60.39	$60.40	$60.40
7 purchase totals =	$535.84		$586.0512	$586.05	$586.05	$586.10