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	$150.43	12.575%	$169.3466	$169.35	$169.35	$169.30
Purchase #2	$200.35	4.527%	$209.4198	$209.42	$209.40	$209.40
Purchase #3	$68.85	13.343%	$78.0367	$78.04	$78.05	$78.00
Purchase #4	$99.25	11.873%	$111.034	$111.03	$111.05	$111.00
Purchase #5	$113.62	3.255%	$117.3183	$117.32	$117.30	$117.30
Purchase #6	$239.37	8.115%	$258.7949	$258.79	$258.80	$258.80
Purchase #7	$70.54	10.251%	$77.7711	$77.77	$77.75	$77.80
7 purchase totals =	$942.41		$1,021.7214	$1,021.72	$1,021.70	$1,021.60