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	$124.49	4.331%	$129.8817	$129.88	$129.90	$129.90
Purchase #2	$240.31	5.836%	$254.3345	$254.33	$254.35	$254.30
Purchase #3	$30.82	7.275%	$33.0622	$33.06	$33.05	$33.10
Purchase #4	$85.45	11.175%	$94.999	$95.00	$95.00	$95.00
Purchase #5	$238.40	3.856%	$247.5927	$247.59	$247.60	$247.60
Purchase #6	$55.60	7.236%	$59.6232	$59.62	$59.60	$59.60
Purchase #7	$241.83	10.583%	$267.4229	$267.42	$267.40	$267.40
7 purchase totals =	$1,016.90		$1,086.9162	$1,086.90	$1,086.90	$1,086.90