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	$197.44	3.487%	$204.3247	$204.32	$204.30	$204.30
Purchase #2	$141.96	7.643%	$152.81	$152.81	$152.80	$152.80
Purchase #3	$60.31	11.815%	$67.4356	$67.44	$67.45	$67.40
Purchase #4	$92.33	9.455%	$101.0598	$101.06	$101.05	$101.10
Purchase #5	$225.26	10.681%	$249.32	$249.32	$249.30	$249.30
Purchase #6	$199.78	13.410%	$226.5705	$226.57	$226.55	$226.60
Purchase #7	$100.68	3.261%	$103.9632	$103.96	$103.95	$104.00
7 purchase totals =	$1,017.76		$1,105.4838	$1,105.48	$1,105.40	$1,105.50