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	$82.39	4.268%	$85.9064	$85.91	$85.90	$85.90
Purchase #2	$55.96	10.196%	$61.6657	$61.67	$61.65	$61.70
Purchase #3	$45.30	11.191%	$50.3695	$50.37	$50.35	$50.40
Purchase #4	$71.35	3.148%	$73.5961	$73.60	$73.60	$73.60
Purchase #5	$143.50	11.503%	$160.0068	$160.01	$160.00	$160.00
Purchase #6	$131.83	8.773%	$143.3954	$143.40	$143.40	$143.40
Purchase #7	$51.43	9.550%	$56.3416	$56.34	$56.35	$56.30
7 purchase totals =	$581.76		$631.2815	$631.30	$631.25	$631.30