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	$244.96	10.176%	$269.8871	$269.89	$269.90	$269.90
Purchase #2	$34.70	11.253%	$38.6048	$38.60	$38.60	$38.60
Purchase #3	$58.61	4.252%	$61.1021	$61.10	$61.10	$61.10
Purchase #4	$56.51	5.825%	$59.8017	$59.80	$59.80	$59.80
Purchase #5	$107.73	8.217%	$116.5822	$116.58	$116.60	$116.60
Purchase #6	$90.63	3.836%	$94.1066	$94.11	$94.10	$94.10
Purchase #7	$195.97	4.719%	$205.2178	$205.22	$205.20	$205.20
7 purchase totals =	$789.11		$845.3023	$845.30	$845.30	$845.30