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	$36.86	4.515%	$38.5242	$38.52	$38.50	$38.50
Purchase #2	$84.57	8.738%	$91.9597	$91.96	$91.95	$92.00
Purchase #3	$43.67	6.554%	$46.5321	$46.53	$46.55	$46.50
Purchase #4	$221.59	3.539%	$229.4321	$229.43	$229.45	$229.40
Purchase #5	$35.52	11.526%	$39.614	$39.61	$39.60	$39.60
Purchase #6	$162.32	8.220%	$175.6627	$175.66	$175.65	$175.70
Purchase #7	$142.56	6.842%	$152.314	$152.31	$152.30	$152.30
7 purchase totals =	$727.09		$774.0388	$774.02	$774.00	$774.00