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	$165.30	8.696%	$179.6745	$179.67	$179.65	$179.70
Purchase #2	$192.65	7.181%	$206.4842	$206.48	$206.50	$206.50
Purchase #3	$21.38	11.399%	$23.8171	$23.82	$23.80	$23.80
Purchase #4	$222.97	9.288%	$243.6795	$243.68	$243.70	$243.70
Purchase #5	$134.71	13.247%	$152.555	$152.56	$152.55	$152.60
Purchase #6	$86.34	3.632%	$89.4759	$89.48	$89.50	$89.50
Purchase #7	$44.69	5.552%	$47.1712	$47.17	$47.15	$47.20
7 purchase totals =	$868.04		$942.8574	$942.86	$942.85	$943.00