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	$60.50	10.871%	$67.077	$67.08	$67.10	$67.10
Purchase #2	$185.78	10.487%	$205.2627	$205.26	$205.25	$205.30
Purchase #3	$29.62	13.280%	$33.5535	$33.55	$33.55	$33.60
Purchase #4	$166.38	8.117%	$179.8851	$179.89	$179.90	$179.90
Purchase #5	$134.88	12.771%	$152.1055	$152.11	$152.10	$152.10
Purchase #6	$187.37	6.536%	$199.6165	$199.62	$199.60	$199.60
Purchase #7	$62.53	12.795%	$70.5307	$70.53	$70.55	$70.50
7 purchase totals =	$827.06		$908.0310	$908.04	$908.05	$908.10