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	$67.32	13.763%	$76.5853	$76.59	$76.60	$76.60
Purchase #2	$156.34	10.740%	$173.1309	$173.13	$173.15	$173.10
Purchase #3	$241.76	3.649%	$250.5818	$250.58	$250.60	$250.60
Purchase #4	$188.80	8.345%	$204.5554	$204.56	$204.55	$204.60
Purchase #5	$64.71	8.753%	$70.3741	$70.37	$70.35	$70.40
Purchase #6	$201.61	13.664%	$229.158	$229.16	$229.15	$229.20
Purchase #7	$171.36	8.229%	$185.4612	$185.46	$185.45	$185.50
7 purchase totals =	$1,091.90		$1,189.8467	$1,189.85	$1,189.85	$1,190.00