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	$127.87	12.174%	$143.4369	$143.44	$143.45	$143.40
Purchase #2	$115.42	10.441%	$127.471	$127.47	$127.45	$127.50
Purchase #3	$115.47	10.159%	$127.2006	$127.20	$127.20	$127.20
Purchase #4	$236.29	13.843%	$268.9996	$269.00	$269.00	$269.00
Purchase #5	$155.53	11.296%	$173.0987	$173.10	$173.10	$173.10
Purchase #6	$87.41	10.766%	$96.8206	$96.82	$96.80	$96.80
Purchase #7	$200.73	7.560%	$215.9052	$215.91	$215.90	$215.90
7 purchase totals =	$1,038.72		$1,152.9326	$1,152.94	$1,152.90	$1,152.90