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	$234.38	4.605%	$245.1732	$245.17	$245.15	$245.20
Purchase #2	$128.82	10.353%	$142.1567	$142.16	$142.15	$142.20
Purchase #3	$160.60	12.380%	$180.4823	$180.48	$180.50	$180.50
Purchase #4	$171.79	8.250%	$185.9627	$185.96	$185.95	$186.00
Purchase #5	$144.55	13.537%	$164.1177	$164.12	$164.10	$164.10
Purchase #6	$201.74	7.139%	$216.1422	$216.14	$216.15	$216.10
Purchase #7	$101.43	11.801%	$113.3998	$113.40	$113.40	$113.40
7 purchase totals =	$1,143.31		$1,247.4346	$1,247.43	$1,247.40	$1,247.50