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	$153.79	7.235%	$164.9167	$164.92	$164.90	$164.90
Purchase #2	$126.61	5.304%	$133.3254	$133.33	$133.35	$133.30
Purchase #3	$59.58	13.529%	$67.6406	$67.64	$67.65	$67.60
Purchase #4	$215.69	13.332%	$244.4458	$244.45	$244.45	$244.40
Purchase #5	$38.73	9.235%	$42.3067	$42.31	$42.30	$42.30
Purchase #6	$130.63	4.705%	$136.7761	$136.78	$136.80	$136.80
Purchase #7	$171.41	13.230%	$194.0875	$194.09	$194.10	$194.10
7 purchase totals =	$896.44		$983.4988	$983.52	$983.55	$983.40