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	$85.75	13.496%	$97.3228	$97.32	$97.30	$97.30
Purchase #2	$95.74	8.370%	$103.7534	$103.75	$103.75	$103.80
Purchase #3	$179.61	11.512%	$200.2867	$200.29	$200.30	$200.30
Purchase #4	$220.74	10.467%	$243.8449	$243.84	$243.85	$243.80
Purchase #5	$174.82	3.867%	$181.5803	$181.58	$181.60	$181.60
Purchase #6	$216.90	4.688%	$227.0683	$227.07	$227.05	$227.10
Purchase #7	$91.47	5.320%	$96.3362	$96.34	$96.35	$96.30
7 purchase totals =	$1,065.03		$1,150.1926	$1,150.19	$1,150.20	$1,150.20