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	$205.87	8.624%	$223.6242	$223.62	$223.60	$223.60
Purchase #2	$102.63	8.524%	$111.3782	$111.38	$111.40	$111.40
Purchase #3	$196.88	9.583%	$215.747	$215.75	$215.75	$215.70
Purchase #4	$173.95	4.616%	$181.9795	$181.98	$182.00	$182.00
Purchase #5	$201.76	4.286%	$210.4074	$210.41	$210.40	$210.40
Purchase #6	$16.51	11.783%	$18.4554	$18.46	$18.45	$18.50
Purchase #7	$161.35	13.674%	$183.413	$183.41	$183.40	$183.40
7 purchase totals =	$1,058.95		$1,145.0047	$1,145.01	$1,145.00	$1,145.00