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	$96.63	5.690%	$102.1282	$102.13	$102.15	$102.10
Purchase #2	$124.60	5.754%	$131.7695	$131.77	$131.75	$131.80
Purchase #3	$112.69	12.175%	$126.41	$126.41	$126.40	$126.40
Purchase #4	$147.43	3.674%	$152.8466	$152.85	$152.85	$152.80
Purchase #5	$75.65	3.394%	$78.2176	$78.22	$78.20	$78.20
Purchase #6	$141.45	3.197%	$145.9722	$145.97	$145.95	$146.00
Purchase #7	$183.96	3.802%	$190.9542	$190.95	$190.95	$191.00
7 purchase totals =	$882.41		$928.2983	$928.30	$928.25	$928.30