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	$156.82	3.641%	$162.5298	$162.53	$162.55	$162.50
Purchase #2	$109.91	9.650%	$120.5163	$120.52	$120.50	$120.50
Purchase #3	$36.89	9.549%	$40.4126	$40.41	$40.40	$40.40
Purchase #4	$96.77	13.166%	$109.5107	$109.51	$109.50	$109.50
Purchase #5	$73.39	7.200%	$78.6741	$78.67	$78.65	$78.70
Purchase #6	$63.82	13.820%	$72.6399	$72.64	$72.65	$72.60
Purchase #7	$147.65	7.151%	$158.2085	$158.21	$158.20	$158.20
7 purchase totals =	$685.25		$742.4919	$742.49	$742.45	$742.40