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	$150.36	11.268%	$167.3026	$167.30	$167.30	$167.30
Purchase #2	$182.87	3.795%	$189.8099	$189.81	$189.80	$189.80
Purchase #3	$171.29	12.253%	$192.2782	$192.28	$192.30	$192.30
Purchase #4	$85.47	4.397%	$89.2281	$89.23	$89.25	$89.20
Purchase #5	$53.90	11.738%	$60.2268	$60.23	$60.25	$60.20
Purchase #6	$176.41	10.181%	$194.3703	$194.37	$194.35	$194.40
Purchase #7	$223.57	6.632%	$238.3972	$238.40	$238.40	$238.40
7 purchase totals =	$1,043.87		$1,131.6131	$1,131.62	$1,131.65	$1,131.60