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	$174.48	9.630%	$191.2824	$191.28	$191.30	$191.30
Purchase #2	$64.37	9.591%	$70.5437	$70.54	$70.55	$70.50
Purchase #3	$181.92	12.780%	$205.1694	$205.17	$205.15	$205.20
Purchase #4	$94.56	5.583%	$99.8393	$99.84	$99.85	$99.80
Purchase #5	$27.41	7.833%	$29.557	$29.56	$29.55	$29.60
Purchase #6	$219.51	3.441%	$227.0633	$227.06	$227.05	$227.10
Purchase #7	$154.26	11.195%	$171.5294	$171.53	$171.55	$171.50
7 purchase totals =	$916.51		$994.9845	$994.98	$995.00	$995.00