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	$54.30	12.848%	$61.2765	$61.28	$61.30	$61.30
Purchase #2	$242.76	9.482%	$265.7785	$265.78	$265.80	$265.80
Purchase #3	$136.38	10.323%	$150.4585	$150.46	$150.45	$150.50
Purchase #4	$45.51	9.242%	$49.716	$49.72	$49.70	$49.70
Purchase #5	$23.27	3.145%	$24.0018	$24.00	$24.00	$24.00
Purchase #6	$123.56	5.238%	$130.0321	$130.03	$130.05	$130.00
Purchase #7	$182.76	6.280%	$194.2373	$194.24	$194.25	$194.20
7 purchase totals =	$808.54		$875.5007	$875.51	$875.55	$875.50