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	$118.68	10.618%	$131.2814	$131.28	$131.30	$131.30
Purchase #2	$215.47	13.801%	$245.207	$245.21	$245.20	$245.20
Purchase #3	$45.69	11.319%	$50.8617	$50.86	$50.85	$50.90
Purchase #4	$167.87	3.807%	$174.2608	$174.26	$174.25	$174.30
Purchase #5	$153.55	13.510%	$174.2946	$174.29	$174.30	$174.30
Purchase #6	$44.78	10.638%	$49.5437	$49.54	$49.55	$49.50
Purchase #7	$170.46	12.529%	$191.8169	$191.82	$191.80	$191.80
7 purchase totals =	$916.50		$1,017.2661	$1,017.26	$1,017.25	$1,017.30