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	$130.86	4.652%	$136.9476	$136.95	$136.95	$136.90
Purchase #2	$172.90	10.131%	$190.4165	$190.42	$190.40	$190.40
Purchase #3	$66.53	7.600%	$71.5863	$71.59	$71.60	$71.60
Purchase #4	$63.62	12.156%	$71.3536	$71.35	$71.35	$71.40
Purchase #5	$115.62	10.163%	$127.3705	$127.37	$127.35	$127.40
Purchase #6	$57.92	7.379%	$62.1939	$62.19	$62.20	$62.20
Purchase #7	$91.95	9.552%	$100.7331	$100.73	$100.75	$100.70
7 purchase totals =	$699.40		$760.6015	$760.60	$760.60	$760.60