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	$176.41	8.339%	$191.1208	$191.12	$191.10	$191.10
Purchase #2	$108.51	3.668%	$112.4901	$112.49	$112.50	$112.50
Purchase #3	$130.68	8.609%	$141.9302	$141.93	$141.95	$141.90
Purchase #4	$239.56	13.104%	$270.9519	$270.95	$270.95	$271.00
Purchase #5	$38.27	6.167%	$40.6301	$40.63	$40.65	$40.60
Purchase #6	$187.45	4.846%	$196.5338	$196.53	$196.55	$196.50
Purchase #7	$175.83	10.395%	$194.1075	$194.11	$194.10	$194.10
7 purchase totals =	$1,056.71		$1,147.7644	$1,147.76	$1,147.80	$1,147.70