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	$215.53	4.853%	$225.9897	$225.99	$226.00	$226.00
Purchase #2	$19.89	3.107%	$20.508	$20.51	$20.50	$20.50
Purchase #3	$91.42	3.413%	$94.5402	$94.54	$94.55	$94.50
Purchase #4	$64.55	12.298%	$72.4884	$72.49	$72.50	$72.50
Purchase #5	$170.45	6.693%	$181.8582	$181.86	$181.85	$181.90
Purchase #6	$94.45	5.115%	$99.2811	$99.28	$99.30	$99.30
Purchase #7	$12.98	8.569%	$14.0923	$14.09	$14.10	$14.10
7 purchase totals =	$669.27		$708.7579	$708.76	$708.80	$708.80