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	$74.31	4.428%	$77.6004	$77.60	$77.60	$77.60
Purchase #2	$141.95	5.716%	$150.0639	$150.06	$150.05	$150.10
Purchase #3	$168.96	10.807%	$187.2195	$187.22	$187.20	$187.20
Purchase #4	$212.42	4.709%	$222.4229	$222.42	$222.40	$222.40
Purchase #5	$153.63	9.566%	$168.3262	$168.33	$168.35	$168.30
Purchase #6	$238.58	8.606%	$259.1122	$259.11	$259.10	$259.10
Purchase #7	$38.36	6.656%	$40.9132	$40.91	$40.90	$40.90
7 purchase totals =	$1,028.21		$1,105.6583	$1,105.65	$1,105.60	$1,105.60