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	$49.73	8.741%	$54.0769	$54.08	$54.10	$54.10
Purchase #2	$94.93	5.153%	$99.8217	$99.82	$99.80	$99.80
Purchase #3	$133.68	11.191%	$148.6401	$148.64	$148.65	$148.60
Purchase #4	$103.52	7.802%	$111.5966	$111.60	$111.60	$111.60
Purchase #5	$229.99	6.629%	$245.236	$245.24	$245.25	$245.20
Purchase #6	$173.39	4.729%	$181.5896	$181.59	$181.60	$181.60
Purchase #7	$64.94	4.386%	$67.7883	$67.79	$67.80	$67.80
7 purchase totals =	$850.18		$908.7492	$908.76	$908.80	$908.70