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	$177.40	5.693%	$187.4994	$187.50	$187.50	$187.50
Purchase #2	$33.67	12.482%	$37.8727	$37.87	$37.85	$37.90
Purchase #3	$177.67	7.106%	$190.2952	$190.30	$190.30	$190.30
Purchase #4	$129.36	10.467%	$142.9001	$142.90	$142.90	$142.90
Purchase #5	$215.72	8.168%	$233.34	$233.34	$233.35	$233.30
Purchase #6	$102.64	12.150%	$115.1108	$115.11	$115.10	$115.10
Purchase #7	$196.30	4.612%	$205.3534	$205.35	$205.35	$205.40
7 purchase totals =	$1,032.76		$1,112.3716	$1,112.37	$1,112.35	$1,112.40