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	$129.30	13.261%	$146.4465	$146.45	$146.45	$146.40
Purchase #2	$157.53	4.427%	$164.5039	$164.50	$164.50	$164.50
Purchase #3	$99.72	5.576%	$105.2804	$105.28	$105.30	$105.30
Purchase #4	$88.98	9.542%	$97.4705	$97.47	$97.45	$97.50
Purchase #5	$126.77	13.693%	$144.1286	$144.13	$144.15	$144.10
Purchase #6	$238.89	4.806%	$250.3711	$250.37	$250.35	$250.40
Purchase #7	$195.55	9.254%	$213.6462	$213.65	$213.65	$213.60
7 purchase totals =	$1,036.74		$1,121.8472	$1,121.85	$1,121.85	$1,121.80