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	$40.53	3.364%	$41.8934	$41.89	$41.90	$41.90
Purchase #2	$62.59	11.636%	$69.873	$69.87	$69.85	$69.90
Purchase #3	$187.26	10.810%	$207.5028	$207.50	$207.50	$207.50
Purchase #4	$98.28	11.858%	$109.934	$109.93	$109.95	$109.90
Purchase #5	$96.69	7.538%	$103.9785	$103.98	$104.00	$104.00
Purchase #6	$219.93	3.231%	$227.0359	$227.04	$227.05	$227.00
Purchase #7	$168.86	12.596%	$190.1296	$190.13	$190.15	$190.10
7 purchase totals =	$874.14		$950.3472	$950.34	$950.40	$950.30