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	$125.38	13.855%	$142.7514	$142.75	$142.75	$142.80
Purchase #2	$114.48	13.270%	$129.6715	$129.67	$129.65	$129.70
Purchase #3	$89.59	12.616%	$100.8927	$100.89	$100.90	$100.90
Purchase #4	$237.30	3.384%	$245.3302	$245.33	$245.35	$245.30
Purchase #5	$13.28	10.735%	$14.7056	$14.71	$14.70	$14.70
Purchase #6	$78.69	3.466%	$81.4174	$81.42	$81.40	$81.40
Purchase #7	$175.83	3.253%	$181.5497	$181.55	$181.55	$181.50
7 purchase totals =	$834.55		$896.3185	$896.32	$896.30	$896.30