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	$54.45	8.858%	$59.2732	$59.27	$59.25	$59.30
Purchase #2	$248.37	9.334%	$271.5529	$271.55	$271.55	$271.60
Purchase #3	$86.33	11.575%	$96.3227	$96.32	$96.30	$96.30
Purchase #4	$178.47	11.155%	$198.3783	$198.38	$198.40	$198.40
Purchase #5	$55.66	5.192%	$58.5499	$58.55	$58.55	$58.50
Purchase #6	$209.43	12.860%	$236.3627	$236.36	$236.35	$236.40
Purchase #7	$52.72	13.262%	$59.7117	$59.71	$59.70	$59.70
7 purchase totals =	$885.43		$980.1514	$980.14	$980.10	$980.20