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	$49.59	10.545%	$54.8193	$54.82	$54.80	$54.80
Purchase #2	$198.59	12.775%	$223.9599	$223.96	$223.95	$224.00
Purchase #3	$63.89	12.474%	$71.8596	$71.86	$71.85	$71.90
Purchase #4	$220.40	13.208%	$249.5104	$249.51	$249.50	$249.50
Purchase #5	$140.75	3.646%	$145.8817	$145.88	$145.90	$145.90
Purchase #6	$70.52	3.751%	$73.1652	$73.17	$73.15	$73.20
Purchase #7	$223.91	7.477%	$240.6518	$240.65	$240.65	$240.70
7 purchase totals =	$967.65		$1,059.8479	$1,059.85	$1,059.80	$1,060.00