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	$84.93	4.800%	$89.0066	$89.01	$89.00	$89.00
Purchase #2	$104.72	5.524%	$110.5047	$110.50	$110.50	$110.50
Purchase #3	$208.55	9.729%	$228.8398	$228.84	$228.85	$228.80
Purchase #4	$76.43	7.483%	$82.1493	$82.15	$82.15	$82.10
Purchase #5	$165.28	9.400%	$180.8163	$180.82	$180.80	$180.80
Purchase #6	$154.93	4.810%	$162.3821	$162.38	$162.40	$162.40
Purchase #7	$65.69	5.616%	$69.3792	$69.38	$69.40	$69.40
7 purchase totals =	$860.53		$923.0780	$923.08	$923.10	$923.00