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	$33.33	8.441%	$36.1434	$36.14	$36.15	$36.10
Purchase #2	$40.90	8.579%	$44.4088	$44.41	$44.40	$44.40
Purchase #3	$126.25	4.632%	$132.0979	$132.10	$132.10	$132.10
Purchase #4	$91.50	5.198%	$96.2562	$96.26	$96.25	$96.30
Purchase #5	$178.47	4.240%	$186.0371	$186.04	$186.05	$186.00
Purchase #6	$174.89	12.341%	$196.4732	$196.47	$196.45	$196.50
Purchase #7	$144.35	6.627%	$153.9161	$153.92	$153.90	$153.90
7 purchase totals =	$789.69		$845.3327	$845.34	$845.30	$845.30