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	$199.77	4.614%	$208.9874	$208.99	$209.00	$209.00
Purchase #2	$220.86	9.615%	$242.0957	$242.10	$242.10	$242.10
Purchase #3	$223.33	6.777%	$238.4651	$238.47	$238.45	$238.50
Purchase #4	$59.37	3.227%	$61.2859	$61.29	$61.30	$61.30
Purchase #5	$135.27	3.144%	$139.5229	$139.52	$139.50	$139.50
Purchase #6	$139.97	13.215%	$158.467	$158.47	$158.45	$158.50
Purchase #7	$93.25	6.831%	$99.6199	$99.62	$99.60	$99.60
7 purchase totals =	$1,071.82		$1,148.4439	$1,148.46	$1,148.40	$1,148.50