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	$198.86	6.106%	$211.0024	$211.00	$211.00	$211.00
Purchase #2	$53.67	10.244%	$59.168	$59.17	$59.15	$59.20
Purchase #3	$166.83	7.246%	$178.9185	$178.92	$178.90	$178.90
Purchase #4	$215.33	3.275%	$222.3821	$222.38	$222.40	$222.40
Purchase #5	$244.58	13.612%	$277.8722	$277.87	$277.85	$277.90
Purchase #6	$72.90	7.453%	$78.3332	$78.33	$78.35	$78.30
Purchase #7	$172.31	8.705%	$187.3096	$187.31	$187.30	$187.30
7 purchase totals =	$1,124.48		$1,214.9860	$1,214.98	$1,214.95	$1,215.00