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	$127.72	7.618%	$137.4497	$137.45	$137.45	$137.40
Purchase #2	$239.93	5.649%	$253.4836	$253.48	$253.50	$253.50
Purchase #3	$64.30	8.741%	$69.9205	$69.92	$69.90	$69.90
Purchase #4	$33.45	10.811%	$37.0663	$37.07	$37.05	$37.10
Purchase #5	$159.64	8.648%	$173.4457	$173.45	$173.45	$173.40
Purchase #6	$245.86	8.734%	$267.3334	$267.33	$267.35	$267.30
Purchase #7	$68.86	13.746%	$78.3255	$78.33	$78.35	$78.30
7 purchase totals =	$939.76		$1,017.0247	$1,017.03	$1,017.05	$1,016.90