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	$42.57	13.870%	$48.4745	$48.47	$48.45	$48.50
Purchase #2	$6.98	3.626%	$7.2331	$7.23	$7.25	$7.20
Purchase #3	$73.89	6.803%	$78.9167	$78.92	$78.90	$78.90
Purchase #4	$68.99	13.521%	$78.3181	$78.32	$78.30	$78.30
Purchase #5	$39.82	12.349%	$44.7374	$44.74	$44.75	$44.70
Purchase #6	$200.82	3.499%	$207.8467	$207.85	$207.85	$207.80
Purchase #7	$90.79	7.399%	$97.5076	$97.51	$97.50	$97.50
7 purchase totals =	$523.86		$563.0341	$563.04	$563.00	$562.90