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	$218.40	3.121%	$225.2163	$225.22	$225.20	$225.20
Purchase #2	$66.71	9.212%	$72.8553	$72.86	$72.85	$72.90
Purchase #3	$133.38	10.714%	$147.6703	$147.67	$147.65	$147.70
Purchase #4	$166.88	11.801%	$186.5735	$186.57	$186.55	$186.60
Purchase #5	$244.37	8.386%	$264.8629	$264.86	$264.85	$264.90
Purchase #6	$137.86	11.122%	$153.1928	$153.19	$153.20	$153.20
Purchase #7	$91.62	12.800%	$103.3474	$103.35	$103.35	$103.30
7 purchase totals =	$1,059.22		$1,153.7185	$1,153.72	$1,153.65	$1,153.80