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	$160.40	4.681%	$167.9083	$167.91	$167.90	$167.90
Purchase #2	$235.37	3.426%	$243.4338	$243.43	$243.45	$243.40
Purchase #3	$6.51	13.532%	$7.3909	$7.39	$7.40	$7.40
Purchase #4	$131.63	8.558%	$142.8949	$142.89	$142.90	$142.90
Purchase #5	$42.27	9.679%	$46.3613	$46.36	$46.35	$46.40
Purchase #6	$209.85	8.352%	$227.3767	$227.38	$227.40	$227.40
Purchase #7	$142.37	10.470%	$157.2761	$157.28	$157.30	$157.30
7 purchase totals =	$928.40		$992.6420	$992.64	$992.70	$992.70