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	$58.39	7.528%	$62.7856	$62.79	$62.80	$62.80
Purchase #2	$154.93	6.176%	$164.4985	$164.50	$164.50	$164.50
Purchase #3	$202.37	8.500%	$219.5715	$219.57	$219.55	$219.60
Purchase #4	$118.96	8.631%	$129.2274	$129.23	$129.25	$129.20
Purchase #5	$183.27	7.103%	$196.2877	$196.29	$196.30	$196.30
Purchase #6	$160.60	11.113%	$178.4475	$178.45	$178.45	$178.40
Purchase #7	$54.69	5.384%	$57.6345	$57.63	$57.65	$57.60
7 purchase totals =	$933.21		$1,008.4527	$1,008.46	$1,008.50	$1,008.40