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	$220.51	11.359%	$245.5577	$245.56	$245.55	$245.60
Purchase #2	$57.80	6.686%	$61.6645	$61.66	$61.65	$61.70
Purchase #3	$170.36	12.671%	$191.9463	$191.95	$191.95	$191.90
Purchase #4	$74.60	5.106%	$78.4091	$78.41	$78.40	$78.40
Purchase #5	$121.48	5.833%	$128.5659	$128.57	$128.55	$128.60
Purchase #6	$161.84	7.721%	$174.3357	$174.34	$174.35	$174.30
Purchase #7	$187.25	5.190%	$196.9683	$196.97	$196.95	$197.00
7 purchase totals =	$993.84		$1,077.4475	$1,077.46	$1,077.40	$1,077.50