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	$29.31	11.653%	$32.7255	$32.73	$32.75	$32.70
Purchase #2	$142.68	10.351%	$157.4488	$157.45	$157.45	$157.40
Purchase #3	$198.36	9.109%	$216.4286	$216.43	$216.45	$216.40
Purchase #4	$185.40	8.249%	$200.6936	$200.69	$200.70	$200.70
Purchase #5	$184.33	6.497%	$196.3059	$196.31	$196.30	$196.30
Purchase #6	$73.38	4.322%	$76.5515	$76.55	$76.55	$76.60
Purchase #7	$167.79	8.584%	$182.1931	$182.19	$182.20	$182.20
7 purchase totals =	$981.25		$1,062.3470	$1,062.35	$1,062.40	$1,062.30