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	$57.82	3.869%	$60.0571	$60.06	$60.05	$60.10
Purchase #2	$50.61	4.595%	$52.9355	$52.94	$52.95	$52.90
Purchase #3	$229.55	8.357%	$248.7335	$248.73	$248.75	$248.70
Purchase #4	$88.98	3.174%	$91.8042	$91.80	$91.80	$91.80
Purchase #5	$104.31	11.547%	$116.3547	$116.35	$116.35	$116.40
Purchase #6	$174.60	10.721%	$193.3189	$193.32	$193.30	$193.30
Purchase #7	$226.25	13.260%	$256.2508	$256.25	$256.25	$256.30
7 purchase totals =	$932.12		$1,019.4547	$1,019.45	$1,019.45	$1,019.50