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	$171.73	13.753%	$195.348	$195.35	$195.35	$195.30
Purchase #2	$229.25	13.640%	$260.5197	$260.52	$260.50	$260.50
Purchase #3	$132.74	4.429%	$138.6191	$138.62	$138.60	$138.60
Purchase #4	$175.57	12.193%	$196.9773	$196.98	$197.00	$197.00
Purchase #5	$82.98	8.274%	$89.8458	$89.85	$89.85	$89.80
Purchase #6	$39.78	10.407%	$43.9199	$43.92	$43.90	$43.90
Purchase #7	$171.33	6.874%	$183.1072	$183.11	$183.10	$183.10
7 purchase totals =	$1,003.38		$1,108.3370	$1,108.35	$1,108.30	$1,108.20