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	$40.87	5.823%	$43.2499	$43.25	$43.25	$43.20
Purchase #2	$107.37	13.464%	$121.8263	$121.83	$121.85	$121.80
Purchase #3	$211.60	12.562%	$238.1812	$238.18	$238.20	$238.20
Purchase #4	$213.73	6.781%	$228.223	$228.22	$228.20	$228.20
Purchase #5	$179.82	6.725%	$191.9129	$191.91	$191.90	$191.90
Purchase #6	$75.70	3.270%	$78.1754	$78.18	$78.20	$78.20
Purchase #7	$100.71	13.472%	$114.2777	$114.28	$114.30	$114.30
7 purchase totals =	$929.80		$1,015.8464	$1,015.85	$1,015.90	$1,015.80