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	$140.52	6.741%	$149.9925	$149.99	$150.00	$150.00
Purchase #2	$114.42	11.321%	$127.3735	$127.37	$127.35	$127.40
Purchase #3	$235.69	11.387%	$262.528	$262.53	$262.55	$262.50
Purchase #4	$155.85	6.156%	$165.4441	$165.44	$165.45	$165.40
Purchase #5	$96.63	13.552%	$109.7253	$109.73	$109.75	$109.70
Purchase #6	$141.61	7.398%	$152.0863	$152.09	$152.10	$152.10
Purchase #7	$181.40	6.303%	$192.8336	$192.83	$192.85	$192.80
7 purchase totals =	$1,066.12		$1,159.9833	$1,159.98	$1,160.05	$1,159.90