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	$243.64	9.817%	$267.5581	$267.56	$267.55	$267.60
Purchase #2	$55.60	6.530%	$59.2307	$59.23	$59.25	$59.20
Purchase #3	$45.79	4.351%	$47.7823	$47.78	$47.80	$47.80
Purchase #4	$241.59	13.132%	$273.3156	$273.32	$273.30	$273.30
Purchase #5	$82.98	3.796%	$86.1299	$86.13	$86.15	$86.10
Purchase #6	$80.99	10.522%	$89.5118	$89.51	$89.50	$89.50
Purchase #7	$75.96	11.393%	$84.6141	$84.61	$84.60	$84.60
7 purchase totals =	$826.55		$908.1425	$908.14	$908.15	$908.10