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	$226.57	3.225%	$233.8769	$233.88	$233.90	$233.90
Purchase #2	$55.48	12.261%	$62.2824	$62.28	$62.30	$62.30
Purchase #3	$156.64	7.777%	$168.8219	$168.82	$168.80	$168.80
Purchase #4	$82.25	7.519%	$88.4344	$88.43	$88.45	$88.40
Purchase #5	$150.43	10.407%	$166.0853	$166.09	$166.10	$166.10
Purchase #6	$224.76	5.598%	$237.3421	$237.34	$237.35	$237.30
Purchase #7	$186.67	12.134%	$209.3205	$209.32	$209.30	$209.30
7 purchase totals =	$1,082.80		$1,166.1635	$1,166.16	$1,166.20	$1,166.10