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	$143.74	12.731%	$162.0395	$162.04	$162.05	$162.00
Purchase #2	$214.35	4.175%	$223.2991	$223.30	$223.30	$223.30
Purchase #3	$79.59	13.296%	$90.1723	$90.17	$90.15	$90.20
Purchase #4	$184.89	5.419%	$194.9092	$194.91	$194.90	$194.90
Purchase #5	$39.56	10.482%	$43.7067	$43.71	$43.70	$43.70
Purchase #6	$86.43	13.613%	$98.1957	$98.20	$98.20	$98.20
Purchase #7	$97.73	6.615%	$104.1948	$104.19	$104.20	$104.20
7 purchase totals =	$846.29		$916.5173	$916.52	$916.50	$916.50