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	$143.45	6.263%	$152.4343	$152.43	$152.45	$152.40
Purchase #2	$81.80	6.112%	$86.7996	$86.80	$86.80	$86.80
Purchase #3	$6.96	13.570%	$7.9045	$7.90	$7.90	$7.90
Purchase #4	$76.47	8.429%	$82.9157	$82.92	$82.90	$82.90
Purchase #5	$195.85	5.466%	$206.5552	$206.56	$206.55	$206.60
Purchase #6	$142.85	8.734%	$155.3265	$155.33	$155.35	$155.30
Purchase #7	$13.74	11.522%	$15.3231	$15.32	$15.30	$15.30
7 purchase totals =	$661.12		$707.2589	$707.26	$707.25	$707.20