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	$157.39	4.666%	$164.7338	$164.73	$164.75	$164.70
Purchase #2	$28.48	4.205%	$29.6776	$29.68	$29.70	$29.70
Purchase #3	$250.60	3.164%	$258.529	$258.53	$258.55	$258.50
Purchase #4	$224.28	6.409%	$238.6541	$238.65	$238.65	$238.70
Purchase #5	$49.58	4.621%	$51.8711	$51.87	$51.85	$51.90
Purchase #6	$67.84	7.625%	$73.0128	$73.01	$73.00	$73.00
Purchase #7	$52.31	13.578%	$59.4127	$59.41	$59.40	$59.40
7 purchase totals =	$830.48		$875.8911	$875.88	$875.90	$875.90