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	$236.83	11.513%	$264.0962	$264.10	$264.10	$264.10
Purchase #2	$38.48	11.544%	$42.9221	$42.92	$42.90	$42.90
Purchase #3	$110.63	11.416%	$123.2595	$123.26	$123.25	$123.30
Purchase #4	$244.92	10.378%	$270.3378	$270.34	$270.35	$270.30
Purchase #5	$108.38	3.117%	$111.7582	$111.76	$111.75	$111.80
Purchase #6	$194.87	10.692%	$215.7055	$215.71	$215.70	$215.70
Purchase #7	$106.81	9.735%	$117.208	$117.21	$117.20	$117.20
7 purchase totals =	$1,040.92		$1,145.2873	$1,145.30	$1,145.25	$1,145.30