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	$137.84	3.254%	$142.3253	$142.33	$142.35	$142.30
Purchase #2	$50.50	4.192%	$52.617	$52.62	$52.60	$52.60
Purchase #3	$79.48	12.817%	$89.667	$89.67	$89.65	$89.70
Purchase #4	$185.67	4.736%	$194.4633	$194.46	$194.45	$194.50
Purchase #5	$112.42	10.473%	$124.1937	$124.19	$124.20	$124.20
Purchase #6	$240.72	13.270%	$272.6635	$272.66	$272.65	$272.70
Purchase #7	$116.79	12.851%	$131.7987	$131.80	$131.80	$131.80
7 purchase totals =	$923.42		$1,007.7285	$1,007.73	$1,007.70	$1,007.80