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	$53.97	13.233%	$61.1119	$61.11	$61.10	$61.10
Purchase #2	$24.60	11.610%	$27.4561	$27.46	$27.45	$27.50
Purchase #3	$202.31	6.695%	$215.8547	$215.85	$215.85	$215.90
Purchase #4	$186.62	11.401%	$207.8965	$207.90	$207.90	$207.90
Purchase #5	$86.98	9.688%	$95.4066	$95.41	$95.40	$95.40
Purchase #6	$48.73	13.611%	$55.3626	$55.36	$55.35	$55.40
Purchase #7	$90.65	11.300%	$100.8935	$100.89	$100.90	$100.90
7 purchase totals =	$693.86		$763.9819	$763.98	$763.95	$764.10