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	$48.94	9.591%	$53.6338	$53.63	$53.65	$53.60
Purchase #2	$40.81	9.279%	$44.5968	$44.60	$44.60	$44.60
Purchase #3	$27.59	10.405%	$30.4607	$30.46	$30.45	$30.50
Purchase #4	$56.42	7.781%	$60.81	$60.81	$60.80	$60.80
Purchase #5	$29.39	7.373%	$31.5569	$31.56	$31.55	$31.60
Purchase #6	$81.44	10.338%	$89.8593	$89.86	$89.85	$89.90
Purchase #7	$17.74	4.281%	$18.4994	$18.50	$18.50	$18.50
7 purchase totals =	$302.33		$329.4169	$329.42	$329.40	$329.50