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	$41.84	6.498%	$44.5588	$44.56	$44.55	$44.60
Purchase #2	$233.98	5.731%	$247.3894	$247.39	$247.40	$247.40
Purchase #3	$74.54	8.466%	$80.8506	$80.85	$80.85	$80.90
Purchase #4	$197.94	6.842%	$211.4831	$211.48	$211.50	$211.50
Purchase #5	$79.51	4.847%	$83.3638	$83.36	$83.35	$83.40
Purchase #6	$179.55	9.494%	$196.5965	$196.60	$196.60	$196.60
Purchase #7	$171.98	3.545%	$178.0767	$178.08	$178.10	$178.10
7 purchase totals =	$979.34		$1,042.3189	$1,042.32	$1,042.35	$1,042.50