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	$179.68	10.398%	$198.3631	$198.36	$198.35	$198.40
Purchase #2	$192.58	12.449%	$216.5543	$216.55	$216.55	$216.60
Purchase #3	$19.27	6.123%	$20.4499	$20.45	$20.45	$20.40
Purchase #4	$180.34	6.478%	$192.0224	$192.02	$192.00	$192.00
Purchase #5	$58.45	11.541%	$65.1957	$65.20	$65.20	$65.20
Purchase #6	$218.27	5.172%	$229.5589	$229.56	$229.55	$229.60
Purchase #7	$169.60	5.287%	$178.5668	$178.57	$178.55	$178.60
7 purchase totals =	$1,018.19		$1,100.7111	$1,100.71	$1,100.65	$1,100.80