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	$10.86	12.654%	$12.2342	$12.23	$12.25	$12.20
Purchase #2	$64.32	13.794%	$73.1923	$73.19	$73.20	$73.20
Purchase #3	$41.34	7.564%	$44.467	$44.47	$44.45	$44.50
Purchase #4	$64.54	12.216%	$72.4242	$72.42	$72.40	$72.40
Purchase #5	$42.27	11.783%	$47.2507	$47.25	$47.25	$47.30
Purchase #6	$158.77	10.681%	$175.7282	$175.73	$175.75	$175.70
Purchase #7	$48.35	7.851%	$52.146	$52.15	$52.15	$52.10
7 purchase totals =	$430.45		$477.4426	$477.44	$477.45	$477.40