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	$175.55	13.379%	$199.0368	$199.04	$199.05	$199.00
Purchase #2	$154.56	3.605%	$160.1319	$160.13	$160.15	$160.10
Purchase #3	$145.92	3.461%	$150.9703	$150.97	$150.95	$151.00
Purchase #4	$96.88	5.740%	$102.4409	$102.44	$102.45	$102.40
Purchase #5	$179.72	11.179%	$199.8109	$199.81	$199.80	$199.80
Purchase #6	$58.92	4.515%	$61.5802	$61.58	$61.60	$61.60
Purchase #7	$66.77	8.279%	$72.2979	$72.30	$72.30	$72.30
7 purchase totals =	$878.32		$946.2689	$946.27	$946.30	$946.20