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	$101.33	3.761%	$105.141	$105.14	$105.15	$105.10
Purchase #2	$188.99	12.319%	$212.2717	$212.27	$212.25	$212.30
Purchase #3	$179.54	9.306%	$196.248	$196.25	$196.25	$196.20
Purchase #4	$215.30	3.534%	$222.9087	$222.91	$222.90	$222.90
Purchase #5	$10.50	12.835%	$11.8477	$11.85	$11.85	$11.80
Purchase #6	$59.69	4.627%	$62.4519	$62.45	$62.45	$62.50
Purchase #7	$237.83	7.483%	$255.6268	$255.63	$255.65	$255.60
7 purchase totals =	$993.18		$1,066.4958	$1,066.50	$1,066.50	$1,066.40