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	$40.52	4.426%	$42.3134	$42.31	$42.30	$42.30
Purchase #2	$121.89	4.511%	$127.3885	$127.39	$127.40	$127.40
Purchase #3	$70.93	9.521%	$77.6832	$77.68	$77.70	$77.70
Purchase #4	$170.32	10.413%	$188.0554	$188.06	$188.05	$188.10
Purchase #5	$11.71	13.288%	$13.266	$13.27	$13.25	$13.30
Purchase #6	$117.44	4.713%	$122.9749	$122.97	$122.95	$123.00
Purchase #7	$167.27	4.282%	$174.4325	$174.43	$174.45	$174.40
7 purchase totals =	$700.08		$746.1139	$746.11	$746.10	$746.20