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	$85.86	4.147%	$89.4206	$89.42	$89.40	$89.40
Purchase #2	$124.98	13.627%	$142.011	$142.01	$142.00	$142.00
Purchase #3	$246.89	4.440%	$257.8519	$257.85	$257.85	$257.90
Purchase #4	$153.67	8.179%	$166.2387	$166.24	$166.25	$166.20
Purchase #5	$122.93	13.476%	$139.496	$139.50	$139.50	$139.50
Purchase #6	$98.80	11.510%	$110.1719	$110.17	$110.15	$110.20
Purchase #7	$103.71	4.851%	$108.741	$108.74	$108.75	$108.70
7 purchase totals =	$936.84		$1,013.9311	$1,013.93	$1,013.90	$1,013.90