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	$125.86	4.459%	$131.4721	$131.47	$131.45	$131.50
Purchase #2	$162.80	3.244%	$168.0812	$168.08	$168.10	$168.10
Purchase #3	$29.92	7.148%	$32.0587	$32.06	$32.05	$32.10
Purchase #4	$104.77	10.449%	$115.7174	$115.72	$115.70	$115.70
Purchase #5	$225.52	12.340%	$253.3492	$253.35	$253.35	$253.30
Purchase #6	$246.84	9.475%	$270.2281	$270.23	$270.25	$270.20
Purchase #7	$41.64	11.206%	$46.3062	$46.31	$46.30	$46.30
7 purchase totals =	$937.35		$1,017.2129	$1,017.22	$1,017.20	$1,017.20