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	$142.71	12.655%	$160.77	$160.77	$160.75	$160.80
Purchase #2	$208.66	7.845%	$225.0294	$225.03	$225.05	$225.00
Purchase #3	$114.54	3.522%	$118.5741	$118.57	$118.55	$118.60
Purchase #4	$228.66	9.710%	$250.8629	$250.86	$250.85	$250.90
Purchase #5	$38.94	8.298%	$42.1712	$42.17	$42.15	$42.20
Purchase #6	$222.30	11.803%	$248.5381	$248.54	$248.55	$248.50
Purchase #7	$220.65	12.565%	$248.3747	$248.37	$248.35	$248.40
7 purchase totals =	$1,176.46		$1,294.3204	$1,294.31	$1,294.25	$1,294.40