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	$185.27	3.720%	$192.162	$192.16	$192.15	$192.20
Purchase #2	$139.98	11.490%	$156.0637	$156.06	$156.05	$156.10
Purchase #3	$150.79	9.194%	$164.6536	$164.65	$164.65	$164.70
Purchase #4	$85.79	5.630%	$90.62	$90.62	$90.60	$90.60
Purchase #5	$109.65	12.647%	$123.5174	$123.52	$123.50	$123.50
Purchase #6	$210.65	9.753%	$231.1947	$231.19	$231.20	$231.20
Purchase #7	$79.88	8.295%	$86.506	$86.51	$86.50	$86.50
7 purchase totals =	$962.01		$1,044.7174	$1,044.71	$1,044.65	$1,044.80