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	$173.88	5.448%	$183.353	$183.35	$183.35	$183.40
Purchase #2	$120.30	6.745%	$128.4142	$128.41	$128.40	$128.40
Purchase #3	$152.47	9.144%	$166.4119	$166.41	$166.40	$166.40
Purchase #4	$214.55	8.645%	$233.0978	$233.10	$233.10	$233.10
Purchase #5	$143.80	3.103%	$148.2621	$148.26	$148.25	$148.30
Purchase #6	$79.47	6.225%	$84.417	$84.42	$84.40	$84.40
Purchase #7	$189.30	3.826%	$196.5426	$196.54	$196.55	$196.50
7 purchase totals =	$1,073.77		$1,140.4986	$1,140.49	$1,140.45	$1,140.50