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	$168.55	9.800%	$185.0679	$185.07	$185.05	$185.10
Purchase #2	$40.74	3.765%	$42.2739	$42.27	$42.25	$42.30
Purchase #3	$43.35	13.515%	$49.2088	$49.21	$49.20	$49.20
Purchase #4	$205.91	4.873%	$215.944	$215.94	$215.95	$215.90
Purchase #5	$64.51	12.756%	$72.7389	$72.74	$72.75	$72.70
Purchase #6	$39.56	8.134%	$42.7778	$42.78	$42.80	$42.80
Purchase #7	$245.94	5.832%	$260.2832	$260.28	$260.30	$260.30
7 purchase totals =	$808.56		$868.2945	$868.29	$868.30	$868.30