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	$11.31	9.685%	$12.4054	$12.41	$12.40	$12.40
Purchase #2	$65.44	12.375%	$73.5382	$73.54	$73.55	$73.50
Purchase #3	$144.75	5.704%	$153.0065	$153.01	$153.00	$153.00
Purchase #4	$134.27	7.401%	$144.2073	$144.21	$144.20	$144.20
Purchase #5	$234.67	10.809%	$260.0355	$260.04	$260.05	$260.00
Purchase #6	$179.36	9.530%	$196.453	$196.45	$196.45	$196.50
Purchase #7	$167.40	13.707%	$190.3455	$190.35	$190.35	$190.30
7 purchase totals =	$937.20		$1,029.9914	$1,030.01	$1,030.00	$1,029.90