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	$132.90	11.559%	$148.2619	$148.26	$148.25	$148.30
Purchase #2	$146.44	10.789%	$162.2394	$162.24	$162.25	$162.20
Purchase #3	$156.93	6.648%	$167.3627	$167.36	$167.35	$167.40
Purchase #4	$39.82	10.173%	$43.8709	$43.87	$43.85	$43.90
Purchase #5	$229.56	6.689%	$244.9153	$244.92	$244.90	$244.90
Purchase #6	$31.68	8.476%	$34.3652	$34.37	$34.35	$34.40
Purchase #7	$49.31	4.142%	$51.3524	$51.35	$51.35	$51.40
7 purchase totals =	$786.64		$852.3678	$852.37	$852.30	$852.50