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	$185.85	11.560%	$207.3343	$207.33	$207.35	$207.30
Purchase #2	$54.87	11.561%	$61.2135	$61.21	$61.20	$61.20
Purchase #3	$199.56	10.157%	$219.8293	$219.83	$219.85	$219.80
Purchase #4	$174.80	9.807%	$191.9426	$191.94	$191.95	$191.90
Purchase #5	$78.78	5.104%	$82.8009	$82.80	$82.80	$82.80
Purchase #6	$64.46	4.425%	$67.3124	$67.31	$67.30	$67.30
Purchase #7	$160.71	11.224%	$178.7481	$178.75	$178.75	$178.70
7 purchase totals =	$919.03		$1,009.1811	$1,009.17	$1,009.20	$1,009.00