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	$29.69	9.423%	$32.4877	$32.49	$32.50	$32.50
Purchase #2	$211.55	5.700%	$223.6084	$223.61	$223.60	$223.60
Purchase #3	$224.44	6.270%	$238.5124	$238.51	$238.50	$238.50
Purchase #4	$28.76	12.173%	$32.261	$32.26	$32.25	$32.30
Purchase #5	$186.51	11.457%	$207.8785	$207.88	$207.90	$207.90
Purchase #6	$58.26	11.245%	$64.8113	$64.81	$64.80	$64.80
Purchase #7	$71.89	7.689%	$77.4176	$77.42	$77.40	$77.40
7 purchase totals =	$811.10		$876.9769	$876.98	$876.95	$877.00