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	$117.38	9.833%	$128.922	$128.92	$128.90	$128.90
Purchase #2	$47.79	13.599%	$54.289	$54.29	$54.30	$54.30
Purchase #3	$198.37	6.501%	$211.266	$211.27	$211.25	$211.30
Purchase #4	$63.86	4.730%	$66.8806	$66.88	$66.90	$66.90
Purchase #5	$25.46	13.261%	$28.8363	$28.84	$28.85	$28.80
Purchase #6	$52.84	13.424%	$59.9332	$59.93	$59.95	$59.90
Purchase #7	$218.37	4.467%	$228.1246	$228.12	$228.10	$228.10
7 purchase totals =	$724.07		$778.2517	$778.25	$778.25	$778.20