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	$178.25	10.140%	$196.3246	$196.32	$196.30	$196.30
Purchase #2	$37.97	8.679%	$41.2654	$41.27	$41.25	$41.30
Purchase #3	$186.55	4.172%	$194.3329	$194.33	$194.35	$194.30
Purchase #4	$215.82	13.723%	$245.437	$245.44	$245.45	$245.40
Purchase #5	$13.35	11.331%	$14.8627	$14.86	$14.85	$14.90
Purchase #6	$142.59	13.309%	$161.5673	$161.57	$161.55	$161.60
Purchase #7	$237.91	4.840%	$249.4248	$249.42	$249.40	$249.40
7 purchase totals =	$1,012.44		$1,103.2147	$1,103.21	$1,103.15	$1,103.20