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	$153.43	3.320%	$158.5239	$158.52	$158.50	$158.50
Purchase #2	$55.33	11.167%	$61.5087	$61.51	$61.50	$61.50
Purchase #3	$192.92	13.196%	$218.3777	$218.38	$218.40	$218.40
Purchase #4	$169.38	13.281%	$191.8754	$191.88	$191.90	$191.90
Purchase #5	$117.96	11.265%	$131.2482	$131.25	$131.25	$131.20
Purchase #6	$232.27	4.130%	$241.8628	$241.86	$241.85	$241.90
Purchase #7	$166.73	8.822%	$181.4389	$181.44	$181.45	$181.40
7 purchase totals =	$1,088.02		$1,184.8356	$1,184.84	$1,184.85	$1,184.80