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	$212.34	7.133%	$227.4862	$227.49	$227.50	$227.50
Purchase #2	$157.33	3.378%	$162.6446	$162.64	$162.65	$162.60
Purchase #3	$233.28	8.586%	$253.3094	$253.31	$253.30	$253.30
Purchase #4	$29.74	7.233%	$31.8911	$31.89	$31.90	$31.90
Purchase #5	$131.91	5.241%	$138.8234	$138.82	$138.80	$138.80
Purchase #6	$161.86	6.603%	$172.5476	$172.55	$172.55	$172.50
Purchase #7	$145.76	4.121%	$151.7668	$151.77	$151.75	$151.80
7 purchase totals =	$1,072.22		$1,138.4691	$1,138.47	$1,138.45	$1,138.40