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	$152.61	6.223%	$162.1069	$162.11	$162.10	$162.10
Purchase #2	$46.91	7.204%	$50.2894	$50.29	$50.30	$50.30
Purchase #3	$69.39	13.116%	$78.4912	$78.49	$78.50	$78.50
Purchase #4	$189.56	10.477%	$209.4202	$209.42	$209.40	$209.40
Purchase #5	$109.98	4.564%	$114.9995	$115.00	$115.00	$115.00
Purchase #6	$189.76	3.324%	$196.0676	$196.07	$196.05	$196.10
Purchase #7	$163.82	8.528%	$177.7906	$177.79	$177.80	$177.80
7 purchase totals =	$922.03		$989.1654	$989.17	$989.15	$989.20