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	$71.31	4.784%	$74.7215	$74.72	$74.70	$74.70
Purchase #2	$77.44	4.633%	$81.0278	$81.03	$81.05	$81.00
Purchase #3	$77.28	12.456%	$86.906	$86.91	$86.90	$86.90
Purchase #4	$217.31	8.400%	$235.564	$235.56	$235.55	$235.60
Purchase #5	$113.45	8.802%	$123.4359	$123.44	$123.45	$123.40
Purchase #6	$210.59	12.704%	$237.3434	$237.34	$237.35	$237.30
Purchase #7	$244.82	11.476%	$272.9155	$272.92	$272.90	$272.90
7 purchase totals =	$1,012.20		$1,111.9141	$1,111.92	$1,111.90	$1,111.80