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	$38.83	7.625%	$41.7908	$41.79	$41.80	$41.80
Purchase #2	$6.33	4.712%	$6.6283	$6.63	$6.65	$6.60
Purchase #3	$62.46	8.596%	$67.8291	$67.83	$67.85	$67.80
Purchase #4	$125.86	3.731%	$130.5558	$130.56	$130.55	$130.60
Purchase #5	$149.43	12.799%	$168.5555	$168.56	$168.55	$168.60
Purchase #6	$162.93	10.874%	$180.647	$180.65	$180.65	$180.60
Purchase #7	$209.71	13.867%	$238.7905	$238.79	$238.80	$238.80
7 purchase totals =	$755.55		$834.7970	$834.81	$834.85	$834.80