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	$111.69	11.156%	$124.1501	$124.15	$124.15	$124.20
Purchase #2	$49.61	11.116%	$55.1246	$55.12	$55.10	$55.10
Purchase #3	$56.89	4.467%	$59.4313	$59.43	$59.45	$59.40
Purchase #4	$194.74	5.710%	$205.8597	$205.86	$205.85	$205.90
Purchase #5	$196.74	9.710%	$215.8435	$215.84	$215.85	$215.80
Purchase #6	$202.46	7.379%	$217.3995	$217.40	$217.40	$217.40
Purchase #7	$141.60	13.134%	$160.1977	$160.20	$160.20	$160.20
7 purchase totals =	$953.73		$1,038.0064	$1,038.00	$1,038.00	$1,038.00