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	$177.76	4.421%	$185.6188	$185.62	$185.60	$185.60
Purchase #2	$133.80	4.348%	$139.6176	$139.62	$139.60	$139.60
Purchase #3	$92.78	11.596%	$103.5388	$103.54	$103.55	$103.50
Purchase #4	$83.99	5.327%	$88.4641	$88.46	$88.45	$88.50
Purchase #5	$92.95	12.641%	$104.6998	$104.70	$104.70	$104.70
Purchase #6	$86.49	7.178%	$92.6983	$92.70	$92.70	$92.70
Purchase #7	$62.82	11.541%	$70.0701	$70.07	$70.05	$70.10
7 purchase totals =	$730.59		$784.7075	$784.71	$784.65	$784.70