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	$172.29	5.195%	$181.2405	$181.24	$181.25	$181.20
Purchase #2	$72.27	12.614%	$81.3861	$81.39	$81.40	$81.40
Purchase #3	$88.75	13.166%	$100.4348	$100.43	$100.45	$100.40
Purchase #4	$58.88	4.383%	$61.4607	$61.46	$61.45	$61.50
Purchase #5	$42.29	5.422%	$44.583	$44.58	$44.60	$44.60
Purchase #6	$211.41	6.251%	$224.6252	$224.63	$224.65	$224.60
Purchase #7	$125.45	7.255%	$134.5514	$134.55	$134.55	$134.60
7 purchase totals =	$771.34		$828.2817	$828.28	$828.35	$828.30