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	$101.58	3.715%	$105.3537	$105.35	$105.35	$105.40
Purchase #2	$170.84	10.568%	$188.8944	$188.89	$188.90	$188.90
Purchase #3	$145.83	7.572%	$156.8722	$156.87	$156.85	$156.90
Purchase #4	$129.45	6.587%	$137.9769	$137.98	$138.00	$138.00
Purchase #5	$157.82	6.796%	$168.5454	$168.55	$168.55	$168.50
Purchase #6	$227.28	12.551%	$255.8059	$255.81	$255.80	$255.80
Purchase #7	$53.53	4.815%	$56.1075	$56.11	$56.10	$56.10
7 purchase totals =	$986.33		$1,069.5560	$1,069.56	$1,069.55	$1,069.60