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	$250.72	13.326%	$284.1309	$284.13	$284.15	$284.10
Purchase #2	$180.56	13.695%	$205.2877	$205.29	$205.30	$205.30
Purchase #3	$43.58	7.458%	$46.8302	$46.83	$46.85	$46.80
Purchase #4	$203.54	9.644%	$223.1694	$223.17	$223.15	$223.20
Purchase #5	$86.69	3.225%	$89.4858	$89.49	$89.50	$89.50
Purchase #6	$106.52	5.144%	$111.9994	$112.00	$112.00	$112.00
Purchase #7	$204.72	9.229%	$223.6136	$223.61	$223.60	$223.60
7 purchase totals =	$1,076.33		$1,184.5170	$1,184.52	$1,184.55	$1,184.50