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	$169.94	4.619%	$177.7895	$177.79	$177.80	$177.80
Purchase #2	$63.35	6.494%	$67.4639	$67.46	$67.45	$67.50
Purchase #3	$172.92	4.320%	$180.3901	$180.39	$180.40	$180.40
Purchase #4	$147.38	3.627%	$152.7255	$152.73	$152.75	$152.70
Purchase #5	$121.31	4.242%	$126.456	$126.46	$126.45	$126.50
Purchase #6	$116.63	9.265%	$127.4358	$127.44	$127.45	$127.40
Purchase #7	$95.68	5.169%	$100.6257	$100.63	$100.65	$100.60
7 purchase totals =	$887.21		$932.8865	$932.90	$932.95	$932.90