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	$31.52	3.217%	$32.534	$32.53	$32.55	$32.50
Purchase #2	$179.54	8.573%	$194.932	$194.93	$194.95	$194.90
Purchase #3	$72.74	7.867%	$78.4625	$78.46	$78.45	$78.50
Purchase #4	$161.72	8.780%	$175.919	$175.92	$175.90	$175.90
Purchase #5	$49.63	3.685%	$51.4589	$51.46	$51.45	$51.50
Purchase #6	$171.91	4.139%	$179.0254	$179.03	$179.05	$179.00
Purchase #7	$29.95	4.463%	$31.2867	$31.29	$31.30	$31.30
7 purchase totals =	$697.01		$743.6185	$743.62	$743.65	$743.60