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	$43.68	4.500%	$45.6456	$45.65	$45.65	$45.60
Purchase #2	$250.54	7.209%	$268.6014	$268.60	$268.60	$268.60
Purchase #3	$96.39	4.675%	$100.8962	$100.90	$100.90	$100.90
Purchase #4	$101.37	11.793%	$113.3246	$113.32	$113.30	$113.30
Purchase #5	$218.99	4.501%	$228.8467	$228.85	$228.85	$228.80
Purchase #6	$141.66	11.505%	$157.958	$157.96	$157.95	$158.00
Purchase #7	$163.40	10.873%	$181.1665	$181.17	$181.15	$181.20
7 purchase totals =	$1,016.03		$1,096.4390	$1,096.45	$1,096.40	$1,096.40