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	$151.80	6.834%	$162.174	$162.17	$162.15	$162.20
Purchase #2	$49.85	12.680%	$56.171	$56.17	$56.15	$56.20
Purchase #3	$112.49	13.587%	$127.774	$127.77	$127.75	$127.80
Purchase #4	$236.59	3.824%	$245.6372	$245.64	$245.65	$245.60
Purchase #5	$239.92	13.377%	$272.0141	$272.01	$272.00	$272.00
Purchase #6	$245.49	7.302%	$263.4157	$263.42	$263.40	$263.40
Purchase #7	$240.78	10.402%	$265.8259	$265.83	$265.85	$265.80
7 purchase totals =	$1,276.92		$1,393.0119	$1,393.01	$1,392.95	$1,393.00