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	$57.38	4.422%	$59.9173	$59.92	$59.90	$59.90
Purchase #2	$194.64	11.619%	$217.2552	$217.26	$217.25	$217.30
Purchase #3	$90.63	4.544%	$94.7482	$94.75	$94.75	$94.70
Purchase #4	$139.36	12.352%	$156.5737	$156.57	$156.55	$156.60
Purchase #5	$226.65	12.858%	$255.7927	$255.79	$255.80	$255.80
Purchase #6	$176.48	11.235%	$196.3075	$196.31	$196.30	$196.30
Purchase #7	$92.48	12.562%	$104.0973	$104.10	$104.10	$104.10
7 purchase totals =	$977.62		$1,084.6919	$1,084.70	$1,084.65	$1,084.70