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	$44.41	12.237%	$49.8445	$49.84	$49.85	$49.80
Purchase #2	$95.80	4.690%	$100.293	$100.29	$100.30	$100.30
Purchase #3	$67.94	4.597%	$71.0632	$71.06	$71.05	$71.10
Purchase #4	$139.28	9.749%	$152.8584	$152.86	$152.85	$152.90
Purchase #5	$231.44	5.108%	$243.262	$243.26	$243.25	$243.30
Purchase #6	$222.27	13.797%	$252.9366	$252.94	$252.95	$252.90
Purchase #7	$217.84	3.473%	$225.4056	$225.41	$225.40	$225.40
7 purchase totals =	$1,018.98		$1,095.6633	$1,095.66	$1,095.65	$1,095.70