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	$48.32	11.458%	$53.8565	$53.86	$53.85	$53.90
Purchase #2	$85.25	9.775%	$93.5832	$93.58	$93.60	$93.60
Purchase #3	$238.50	12.743%	$268.8921	$268.89	$268.90	$268.90
Purchase #4	$207.54	7.499%	$223.1034	$223.10	$223.10	$223.10
Purchase #5	$85.66	4.447%	$89.4693	$89.47	$89.45	$89.50
Purchase #6	$174.44	5.869%	$184.6779	$184.68	$184.70	$184.70
Purchase #7	$64.95	3.529%	$67.2421	$67.24	$67.25	$67.20
7 purchase totals =	$904.66		$980.8245	$980.82	$980.85	$980.90