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	$200.54	5.380%	$211.3291	$211.33	$211.35	$211.30
Purchase #2	$82.62	9.340%	$90.3367	$90.34	$90.35	$90.30
Purchase #3	$24.88	7.162%	$26.6619	$26.66	$26.65	$26.70
Purchase #4	$227.57	6.114%	$241.4836	$241.48	$241.50	$241.50
Purchase #5	$247.49	7.215%	$265.3464	$265.35	$265.35	$265.30
Purchase #6	$65.61	9.402%	$71.7787	$71.78	$71.80	$71.80
Purchase #7	$238.64	9.739%	$261.8811	$261.88	$261.90	$261.90
7 purchase totals =	$1,087.35		$1,168.8175	$1,168.82	$1,168.90	$1,168.80