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	$26.76	4.139%	$27.8676	$27.87	$27.85	$27.90
Purchase #2	$14.67	11.311%	$16.3293	$16.33	$16.35	$16.30
Purchase #3	$193.59	10.455%	$213.8298	$213.83	$213.85	$213.80
Purchase #4	$51.60	6.414%	$54.9096	$54.91	$54.90	$54.90
Purchase #5	$196.34	4.650%	$205.4698	$205.47	$205.45	$205.50
Purchase #6	$79.80	13.441%	$90.5259	$90.53	$90.55	$90.50
Purchase #7	$229.85	8.647%	$249.7251	$249.73	$249.75	$249.70
7 purchase totals =	$792.61		$858.6571	$858.67	$858.70	$858.60