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	$168.60	7.663%	$181.5198	$181.52	$181.50	$181.50
Purchase #2	$100.26	3.160%	$103.4282	$103.43	$103.45	$103.40
Purchase #3	$27.57	4.392%	$28.7809	$28.78	$28.80	$28.80
Purchase #4	$203.83	5.669%	$215.3851	$215.39	$215.40	$215.40
Purchase #5	$246.36	7.309%	$264.3665	$264.37	$264.35	$264.40
Purchase #6	$223.75	6.426%	$238.1282	$238.13	$238.15	$238.10
Purchase #7	$187.89	12.470%	$211.3199	$211.32	$211.30	$211.30
7 purchase totals =	$1,158.26		$1,242.9286	$1,242.94	$1,242.95	$1,242.90