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	$238.94	10.263%	$263.4624	$263.46	$263.45	$263.50
Purchase #2	$67.73	8.723%	$73.6381	$73.64	$73.65	$73.60
Purchase #3	$54.38	3.156%	$56.0962	$56.10	$56.10	$56.10
Purchase #4	$71.91	9.215%	$78.5365	$78.54	$78.55	$78.50
Purchase #5	$210.51	8.107%	$227.576	$227.58	$227.60	$227.60
Purchase #6	$30.68	9.165%	$33.4918	$33.49	$33.50	$33.50
Purchase #7	$145.93	8.113%	$157.7693	$157.77	$157.75	$157.80
7 purchase totals =	$820.08		$890.5703	$890.58	$890.60	$890.60