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	$173.41	13.290%	$196.4562	$196.46	$196.45	$196.50
Purchase #2	$165.80	8.157%	$179.3243	$179.32	$179.30	$179.30
Purchase #3	$58.84	3.419%	$60.8517	$60.85	$60.85	$60.90
Purchase #4	$56.71	5.322%	$59.7281	$59.73	$59.75	$59.70
Purchase #5	$201.92	4.273%	$210.548	$210.55	$210.55	$210.50
Purchase #6	$101.70	10.601%	$112.4812	$112.48	$112.50	$112.50
Purchase #7	$52.66	6.426%	$56.0439	$56.04	$56.05	$56.00
7 purchase totals =	$811.04		$875.4334	$875.43	$875.45	$875.40