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	$168.86	5.515%	$178.1726	$178.17	$178.15	$178.20
Purchase #2	$45.53	4.352%	$47.5115	$47.51	$47.50	$47.50
Purchase #3	$36.78	10.223%	$40.54	$40.54	$40.55	$40.50
Purchase #4	$99.52	8.659%	$108.1374	$108.14	$108.15	$108.10
Purchase #5	$203.81	6.431%	$216.917	$216.92	$216.90	$216.90
Purchase #6	$192.41	12.752%	$216.9461	$216.95	$216.95	$216.90
Purchase #7	$59.33	8.120%	$64.1476	$64.15	$64.15	$64.10
7 purchase totals =	$806.24		$872.3722	$872.38	$872.35	$872.20