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	$170.77	11.826%	$190.9653	$190.97	$190.95	$191.00
Purchase #2	$158.81	8.288%	$171.9722	$171.97	$171.95	$172.00
Purchase #3	$58.84	4.137%	$61.2742	$61.27	$61.25	$61.30
Purchase #4	$237.57	13.786%	$270.3214	$270.32	$270.30	$270.30
Purchase #5	$56.81	8.252%	$61.498	$61.50	$61.50	$61.50
Purchase #6	$81.86	9.331%	$89.4984	$89.50	$89.50	$89.50
Purchase #7	$247.34	4.781%	$259.1653	$259.17	$259.15	$259.20
7 purchase totals =	$1,012.00		$1,104.6948	$1,104.70	$1,104.60	$1,104.80