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	$243.40	7.779%	$262.3341	$262.33	$262.35	$262.30
Purchase #2	$173.45	4.530%	$181.3073	$181.31	$181.30	$181.30
Purchase #3	$117.81	9.360%	$128.837	$128.84	$128.85	$128.80
Purchase #4	$151.45	6.779%	$161.7168	$161.72	$161.70	$161.70
Purchase #5	$60.99	10.757%	$67.5507	$67.55	$67.55	$67.60
Purchase #6	$61.97	4.676%	$64.8677	$64.87	$64.85	$64.90
Purchase #7	$214.75	3.636%	$222.5583	$222.56	$222.55	$222.60
7 purchase totals =	$1,023.82		$1,089.1719	$1,089.18	$1,089.15	$1,089.20