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	$158.96	4.156%	$165.5664	$165.57	$165.55	$165.60
Purchase #2	$29.87	6.657%	$31.8584	$31.86	$31.85	$31.90
Purchase #3	$167.61	10.548%	$185.2895	$185.29	$185.30	$185.30
Purchase #4	$241.85	3.395%	$250.0608	$250.06	$250.05	$250.10
Purchase #5	$145.56	11.794%	$162.7273	$162.73	$162.75	$162.70
Purchase #6	$184.49	8.839%	$200.7971	$200.80	$200.80	$200.80
Purchase #7	$13.36	12.203%	$14.9903	$14.99	$15.00	$15.00
7 purchase totals =	$941.70		$1,011.2898	$1,011.30	$1,011.30	$1,011.40