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	$101.38	12.243%	$113.792	$113.79	$113.80	$113.80
Purchase #2	$207.75	4.378%	$216.8453	$216.85	$216.85	$216.80
Purchase #3	$245.66	6.782%	$262.3207	$262.32	$262.30	$262.30
Purchase #4	$72.93	6.841%	$77.9191	$77.92	$77.90	$77.90
Purchase #5	$52.38	8.118%	$56.6322	$56.63	$56.65	$56.60
Purchase #6	$73.56	9.322%	$80.4173	$80.42	$80.40	$80.40
Purchase #7	$181.59	10.567%	$200.7786	$200.78	$200.80	$200.80
7 purchase totals =	$935.25		$1,008.7052	$1,008.71	$1,008.70	$1,008.60