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	$118.71	4.829%	$124.4425	$124.44	$124.45	$124.40
Purchase #2	$25.42	11.597%	$28.368	$28.37	$28.35	$28.40
Purchase #3	$31.50	13.395%	$35.7194	$35.72	$35.70	$35.70
Purchase #4	$109.42	7.783%	$117.9362	$117.94	$117.95	$117.90
Purchase #5	$242.35	13.204%	$274.3499	$274.35	$274.35	$274.30
Purchase #6	$150.58	9.253%	$164.5132	$164.51	$164.50	$164.50
Purchase #7	$243.32	12.654%	$274.1097	$274.11	$274.10	$274.10
7 purchase totals =	$921.30		$1,019.4389	$1,019.44	$1,019.40	$1,019.30