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	$105.88	3.648%	$109.7425	$109.74	$109.75	$109.70
Purchase #2	$108.38	13.871%	$123.4134	$123.41	$123.40	$123.40
Purchase #3	$177.67	5.782%	$187.9429	$187.94	$187.95	$187.90
Purchase #4	$198.84	8.657%	$216.0536	$216.05	$216.05	$216.10
Purchase #5	$53.30	13.301%	$60.3894	$60.39	$60.40	$60.40
Purchase #6	$157.95	10.684%	$174.8254	$174.83	$174.85	$174.80
Purchase #7	$227.29	12.711%	$256.1808	$256.18	$256.20	$256.20
7 purchase totals =	$1,029.31		$1,128.5480	$1,128.54	$1,128.60	$1,128.50