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	$50.33	9.556%	$55.1395	$55.14	$55.15	$55.10
Purchase #2	$65.72	10.134%	$72.3801	$72.38	$72.40	$72.40
Purchase #3	$223.86	7.721%	$241.1442	$241.14	$241.15	$241.10
Purchase #4	$150.28	5.871%	$159.1029	$159.10	$159.10	$159.10
Purchase #5	$239.30	3.396%	$247.4266	$247.43	$247.45	$247.40
Purchase #6	$244.89	12.267%	$274.9307	$274.93	$274.95	$274.90
Purchase #7	$132.58	11.582%	$147.9354	$147.94	$147.95	$147.90
7 purchase totals =	$1,106.96		$1,198.0594	$1,198.06	$1,198.15	$1,197.90