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	$52.63	11.292%	$58.573	$58.57	$58.55	$58.60
Purchase #2	$146.42	12.710%	$165.03	$165.03	$165.05	$165.00
Purchase #3	$43.71	13.260%	$49.5059	$49.51	$49.50	$49.50
Purchase #4	$74.70	10.438%	$82.4972	$82.50	$82.50	$82.50
Purchase #5	$194.33	3.115%	$200.3834	$200.38	$200.40	$200.40
Purchase #6	$47.88	10.299%	$52.8112	$52.81	$52.80	$52.80
Purchase #7	$159.27	8.153%	$172.2553	$172.26	$172.25	$172.30
7 purchase totals =	$718.94		$781.0560	$781.06	$781.05	$781.10