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	$79.69	5.295%	$83.9096	$83.91	$83.90	$83.90
Purchase #2	$18.94	9.748%	$20.7863	$20.79	$20.80	$20.80
Purchase #3	$98.84	13.711%	$112.392	$112.39	$112.40	$112.40
Purchase #4	$19.33	5.151%	$20.3257	$20.33	$20.35	$20.30
Purchase #5	$151.61	12.772%	$170.9736	$170.97	$170.95	$171.00
Purchase #6	$124.31	13.457%	$141.0384	$141.04	$141.05	$141.00
Purchase #7	$78.54	5.387%	$82.7709	$82.77	$82.75	$82.80
7 purchase totals =	$571.26		$632.1965	$632.20	$632.20	$632.20