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	$5.27	3.513%	$5.4551	$5.46	$5.45	$5.50
Purchase #2	$63.31	11.426%	$70.5438	$70.54	$70.55	$70.50
Purchase #3	$191.55	11.526%	$213.6281	$213.63	$213.65	$213.60
Purchase #4	$180.86	13.777%	$205.7771	$205.78	$205.80	$205.80
Purchase #5	$139.36	4.356%	$145.4305	$145.43	$145.45	$145.40
Purchase #6	$170.86	11.223%	$190.0356	$190.04	$190.05	$190.00
Purchase #7	$214.38	7.552%	$230.57	$230.57	$230.55	$230.60
7 purchase totals =	$965.59		$1,061.4402	$1,061.45	$1,061.50	$1,061.40