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	$70.30	9.276%	$76.821	$76.82	$76.80	$76.80
Purchase #2	$120.73	5.646%	$127.5464	$127.55	$127.55	$127.50
Purchase #3	$188.65	5.245%	$198.5447	$198.54	$198.55	$198.50
Purchase #4	$154.72	6.261%	$164.407	$164.41	$164.40	$164.40
Purchase #5	$250.56	4.696%	$262.3263	$262.33	$262.35	$262.30
Purchase #6	$6.28	12.214%	$7.047	$7.05	$7.05	$7.00
Purchase #7	$104.32	3.660%	$108.1381	$108.14	$108.15	$108.10
7 purchase totals =	$895.56		$944.8305	$944.84	$944.85	$944.60