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	$181.91	9.135%	$198.5275	$198.53	$198.55	$198.50
Purchase #2	$33.71	11.350%	$37.5361	$37.54	$37.55	$37.50
Purchase #3	$46.65	12.341%	$52.4071	$52.41	$52.40	$52.40
Purchase #4	$121.67	5.664%	$128.5614	$128.56	$128.55	$128.60
Purchase #5	$173.54	13.168%	$196.3917	$196.39	$196.40	$196.40
Purchase #6	$123.26	3.239%	$127.2524	$127.25	$127.25	$127.30
Purchase #7	$98.32	9.725%	$107.8816	$107.88	$107.90	$107.90
7 purchase totals =	$779.06		$848.5578	$848.56	$848.60	$848.60