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	$181.94	13.525%	$206.5474	$206.55	$206.55	$206.50
Purchase #2	$76.64	7.697%	$82.539	$82.54	$82.55	$82.50
Purchase #3	$204.49	12.235%	$229.5094	$229.51	$229.50	$229.50
Purchase #4	$149.55	3.195%	$154.3281	$154.33	$154.35	$154.30
Purchase #5	$159.40	5.636%	$168.3838	$168.38	$168.40	$168.40
Purchase #6	$163.39	4.746%	$171.1445	$171.14	$171.15	$171.10
Purchase #7	$87.71	10.299%	$96.7433	$96.74	$96.75	$96.70
7 purchase totals =	$1,023.12		$1,109.1955	$1,109.19	$1,109.25	$1,109.00