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	$103.82	11.717%	$115.9846	$115.98	$116.00	$116.00
Purchase #2	$201.50	10.215%	$222.0832	$222.08	$222.10	$222.10
Purchase #3	$40.96	10.568%	$45.2887	$45.29	$45.30	$45.30
Purchase #4	$166.78	3.695%	$172.9425	$172.94	$172.95	$172.90
Purchase #5	$50.77	8.539%	$55.1053	$55.11	$55.10	$55.10
Purchase #6	$249.73	6.703%	$266.4694	$266.47	$266.45	$266.50
Purchase #7	$65.95	10.339%	$72.7686	$72.77	$72.75	$72.80
7 purchase totals =	$879.51		$950.6423	$950.64	$950.65	$950.70