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	$140.85	5.463%	$148.5446	$148.54	$148.55	$148.50
Purchase #2	$235.66	9.417%	$257.8521	$257.85	$257.85	$257.90
Purchase #3	$64.98	3.808%	$67.4544	$67.45	$67.45	$67.50
Purchase #4	$145.43	5.374%	$153.2454	$153.25	$153.25	$153.20
Purchase #5	$72.85	7.830%	$78.5542	$78.55	$78.55	$78.60
Purchase #6	$240.93	8.423%	$261.2235	$261.22	$261.20	$261.20
Purchase #7	$92.84	11.301%	$103.3318	$103.33	$103.35	$103.30
7 purchase totals =	$993.54		$1,070.2060	$1,070.19	$1,070.20	$1,070.20