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	$36.34	4.385%	$37.9335	$37.93	$37.95	$37.90
Purchase #2	$149.70	7.179%	$160.447	$160.45	$160.45	$160.40
Purchase #3	$158.92	5.339%	$167.4047	$167.40	$167.40	$167.40
Purchase #4	$13.84	6.499%	$14.7395	$14.74	$14.75	$14.70
Purchase #5	$35.81	12.414%	$40.2555	$40.26	$40.25	$40.30
Purchase #6	$5.56	12.651%	$6.2634	$6.26	$6.25	$6.30
Purchase #7	$38.55	12.435%	$43.3437	$43.34	$43.35	$43.30
7 purchase totals =	$438.72		$470.3873	$470.38	$470.40	$470.30