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	$146.34	10.779%	$162.114	$162.11	$162.10	$162.10
Purchase #2	$82.76	4.492%	$86.4776	$86.48	$86.50	$86.50
Purchase #3	$131.37	9.839%	$144.2955	$144.30	$144.30	$144.30
Purchase #4	$45.78	5.692%	$48.3858	$48.39	$48.40	$48.40
Purchase #5	$111.34	5.417%	$117.3713	$117.37	$117.35	$117.40
Purchase #6	$158.98	8.223%	$172.0529	$172.05	$172.05	$172.10
Purchase #7	$91.82	13.789%	$104.4811	$104.48	$104.50	$104.50
7 purchase totals =	$768.39		$835.1782	$835.18	$835.20	$835.30