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	$186.25	7.548%	$200.3082	$200.31	$200.30	$200.30
Purchase #2	$159.72	10.411%	$176.3484	$176.35	$176.35	$176.30
Purchase #3	$155.79	4.354%	$162.5731	$162.57	$162.55	$162.60
Purchase #4	$186.80	4.716%	$195.6095	$195.61	$195.60	$195.60
Purchase #5	$50.54	11.350%	$56.2763	$56.28	$56.30	$56.30
Purchase #6	$196.58	9.525%	$215.3042	$215.30	$215.30	$215.30
Purchase #7	$237.71	11.360%	$264.7139	$264.71	$264.70	$264.70
7 purchase totals =	$1,173.39		$1,271.1336	$1,271.13	$1,271.10	$1,271.10