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	$226.34	10.568%	$250.2596	$250.26	$250.25	$250.30
Purchase #2	$239.60	3.127%	$247.0923	$247.09	$247.10	$247.10
Purchase #3	$187.32	12.269%	$210.3023	$210.30	$210.30	$210.30
Purchase #4	$141.71	13.533%	$160.8876	$160.89	$160.90	$160.90
Purchase #5	$81.54	10.155%	$89.8204	$89.82	$89.80	$89.80
Purchase #6	$22.98	9.864%	$25.2467	$25.25	$25.25	$25.20
Purchase #7	$147.75	13.681%	$167.9637	$167.96	$167.95	$168.00
7 purchase totals =	$1,047.24		$1,151.5726	$1,151.57	$1,151.55	$1,151.60