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	$97.98	3.358%	$101.2702	$101.27	$101.25	$101.30
Purchase #2	$102.45	4.316%	$106.8717	$106.87	$106.85	$106.90
Purchase #3	$211.65	3.678%	$219.4345	$219.43	$219.45	$219.40
Purchase #4	$242.25	8.188%	$262.0854	$262.09	$262.10	$262.10
Purchase #5	$112.66	12.837%	$127.1222	$127.12	$127.10	$127.10
Purchase #6	$156.45	12.446%	$175.9218	$175.92	$175.90	$175.90
Purchase #7	$70.98	3.616%	$73.5466	$73.55	$73.55	$73.50
7 purchase totals =	$994.42		$1,066.2524	$1,066.25	$1,066.20	$1,066.20