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	$173.69	9.410%	$190.0342	$190.03	$190.05	$190.00
Purchase #2	$76.53	12.615%	$86.1843	$86.18	$86.20	$86.20
Purchase #3	$245.91	3.217%	$253.8209	$253.82	$253.80	$253.80
Purchase #4	$64.99	8.552%	$70.5479	$70.55	$70.55	$70.50
Purchase #5	$81.61	10.589%	$90.2517	$90.25	$90.25	$90.30
Purchase #6	$125.40	13.442%	$142.2563	$142.26	$142.25	$142.30
Purchase #7	$175.86	4.282%	$183.3903	$183.39	$183.40	$183.40
7 purchase totals =	$943.99		$1,016.4856	$1,016.48	$1,016.50	$1,016.50