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	$45.84	9.243%	$50.077	$50.08	$50.10	$50.10
Purchase #2	$56.40	9.307%	$61.6491	$61.65	$61.65	$61.60
Purchase #3	$47.40	6.798%	$50.6223	$50.62	$50.60	$50.60
Purchase #4	$184.27	6.683%	$196.5848	$196.58	$196.60	$196.60
Purchase #5	$82.68	9.166%	$90.2584	$90.26	$90.25	$90.30
Purchase #6	$215.51	6.186%	$228.8414	$228.84	$228.85	$228.80
Purchase #7	$67.67	4.234%	$70.5351	$70.54	$70.55	$70.50
7 purchase totals =	$699.77		$748.5681	$748.57	$748.60	$748.50