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	$54.62	8.674%	$59.3577	$59.36	$59.35	$59.40
Purchase #2	$174.56	12.820%	$196.9386	$196.94	$196.95	$196.90
Purchase #3	$239.49	10.207%	$263.9347	$263.93	$263.95	$263.90
Purchase #4	$190.63	13.209%	$215.8103	$215.81	$215.80	$215.80
Purchase #5	$188.61	10.599%	$208.6008	$208.60	$208.60	$208.60
Purchase #6	$175.83	6.563%	$187.3697	$187.37	$187.35	$187.40
Purchase #7	$135.91	9.835%	$149.2767	$149.28	$149.30	$149.30
7 purchase totals =	$1,159.65		$1,281.2885	$1,281.29	$1,281.30	$1,281.30