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	$132.45	11.559%	$147.7599	$147.76	$147.75	$147.80
Purchase #2	$140.63	12.860%	$158.715	$158.72	$158.70	$158.70
Purchase #3	$194.91	7.312%	$209.1618	$209.16	$209.15	$209.20
Purchase #4	$215.75	3.502%	$223.3056	$223.31	$223.30	$223.30
Purchase #5	$64.80	11.204%	$72.0602	$72.06	$72.05	$72.10
Purchase #6	$77.80	10.867%	$86.2545	$86.25	$86.25	$86.30
Purchase #7	$157.38	4.724%	$164.8146	$164.81	$164.80	$164.80
7 purchase totals =	$983.72		$1,062.0716	$1,062.07	$1,062.00	$1,062.20