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	$160.94	6.346%	$171.1533	$171.15	$171.15	$171.20
Purchase #2	$83.64	9.319%	$91.4344	$91.43	$91.45	$91.40
Purchase #3	$104.31	12.276%	$117.1151	$117.12	$117.10	$117.10
Purchase #4	$153.31	9.762%	$168.2761	$168.28	$168.30	$168.30
Purchase #5	$83.32	10.286%	$91.8903	$91.89	$91.90	$91.90
Purchase #6	$211.37	7.334%	$226.8719	$226.87	$226.85	$226.90
Purchase #7	$185.44	8.232%	$200.7054	$200.71	$200.70	$200.70
7 purchase totals =	$982.33		$1,067.4465	$1,067.45	$1,067.45	$1,067.50