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	$43.85	3.801%	$45.5167	$45.52	$45.50	$45.50
Purchase #2	$197.64	7.253%	$211.9748	$211.97	$211.95	$212.00
Purchase #3	$210.91	9.746%	$231.4653	$231.47	$231.45	$231.50
Purchase #4	$77.53	9.661%	$85.0202	$85.02	$85.00	$85.00
Purchase #5	$169.69	7.339%	$182.1435	$182.14	$182.15	$182.10
Purchase #6	$27.78	3.660%	$28.7967	$28.80	$28.80	$28.80
Purchase #7	$211.38	12.415%	$237.6228	$237.62	$237.60	$237.60
7 purchase totals =	$938.78		$1,022.5400	$1,022.54	$1,022.45	$1,022.50