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	$134.85	6.532%	$143.6584	$143.66	$143.65	$143.70
Purchase #2	$227.35	4.711%	$238.0605	$238.06	$238.05	$238.10
Purchase #3	$144.54	12.166%	$162.1247	$162.12	$162.10	$162.10
Purchase #4	$152.80	4.141%	$159.1274	$159.13	$159.15	$159.10
Purchase #5	$99.80	4.303%	$104.0944	$104.09	$104.10	$104.10
Purchase #6	$133.98	7.576%	$144.1303	$144.13	$144.15	$144.10
Purchase #7	$135.71	6.234%	$144.1702	$144.17	$144.15	$144.20
7 purchase totals =	$1,029.03		$1,095.3659	$1,095.36	$1,095.35	$1,095.40