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	$107.41	10.590%	$118.7847	$118.78	$118.80	$118.80
Purchase #2	$144.34	4.560%	$150.9219	$150.92	$150.90	$150.90
Purchase #3	$41.88	6.259%	$44.5013	$44.50	$44.50	$44.50
Purchase #4	$11.31	8.173%	$12.2344	$12.23	$12.25	$12.20
Purchase #5	$61.64	3.668%	$63.901	$63.90	$63.90	$63.90
Purchase #6	$93.39	12.775%	$105.3206	$105.32	$105.30	$105.30
Purchase #7	$12.36	6.142%	$13.1192	$13.12	$13.10	$13.10
7 purchase totals =	$472.33		$508.7831	$508.77	$508.75	$508.70