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	$123.32	6.412%	$131.2273	$131.23	$131.25	$131.20
Purchase #2	$141.98	7.117%	$152.0847	$152.08	$152.10	$152.10
Purchase #3	$115.75	10.607%	$128.0276	$128.03	$128.05	$128.00
Purchase #4	$83.41	8.652%	$90.6266	$90.63	$90.65	$90.60
Purchase #5	$137.35	13.113%	$155.3607	$155.36	$155.35	$155.40
Purchase #6	$116.34	12.522%	$130.9081	$130.91	$130.90	$130.90
Purchase #7	$95.98	11.553%	$107.0686	$107.07	$107.05	$107.10
7 purchase totals =	$814.13		$895.3036	$895.31	$895.35	$895.30