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	$149.50	10.823%	$165.6804	$165.68	$165.70	$165.70
Purchase #2	$242.89	8.296%	$263.0402	$263.04	$263.05	$263.00
Purchase #3	$61.75	4.603%	$64.5924	$64.59	$64.60	$64.60
Purchase #4	$238.80	4.390%	$249.2833	$249.28	$249.30	$249.30
Purchase #5	$207.70	3.524%	$215.0193	$215.02	$215.00	$215.00
Purchase #6	$107.32	3.621%	$111.2061	$111.21	$111.20	$111.20
Purchase #7	$76.49	7.216%	$82.0095	$82.01	$82.00	$82.00
7 purchase totals =	$1,084.45		$1,150.8312	$1,150.83	$1,150.85	$1,150.80