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	$117.66	8.564%	$127.7364	$127.74	$127.75	$127.70
Purchase #2	$166.78	8.457%	$180.8846	$180.88	$180.90	$180.90
Purchase #3	$138.76	10.811%	$153.7613	$153.76	$153.75	$153.80
Purchase #4	$73.73	5.469%	$77.7623	$77.76	$77.75	$77.80
Purchase #5	$250.86	11.685%	$280.173	$280.17	$280.15	$280.20
Purchase #6	$59.54	3.826%	$61.818	$61.82	$61.80	$61.80
Purchase #7	$172.77	12.656%	$194.6358	$194.64	$194.65	$194.60
7 purchase totals =	$980.10		$1,076.7714	$1,076.77	$1,076.75	$1,076.80