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	$90.25	12.598%	$101.6197	$101.62	$101.60	$101.60
Purchase #2	$194.92	5.630%	$205.894	$205.89	$205.90	$205.90
Purchase #3	$207.50	10.439%	$229.1609	$229.16	$229.15	$229.20
Purchase #4	$147.79	5.740%	$156.2731	$156.27	$156.25	$156.30
Purchase #5	$160.59	13.740%	$182.6551	$182.66	$182.65	$182.70
Purchase #6	$49.89	6.308%	$53.0371	$53.04	$53.05	$53.00
Purchase #7	$244.78	8.650%	$265.9535	$265.95	$265.95	$266.00
7 purchase totals =	$1,095.72		$1,194.5934	$1,194.59	$1,194.55	$1,194.70