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	$51.58	7.676%	$55.5393	$55.54	$55.55	$55.50
Purchase #2	$242.59	5.263%	$255.3575	$255.36	$255.35	$255.40
Purchase #3	$212.36	7.455%	$228.1914	$228.19	$228.20	$228.20
Purchase #4	$167.52	7.648%	$180.3319	$180.33	$180.35	$180.30
Purchase #5	$112.55	9.293%	$123.0093	$123.01	$123.00	$123.00
Purchase #6	$152.61	12.345%	$171.4497	$171.45	$171.45	$171.40
Purchase #7	$94.88	5.283%	$99.8925	$99.89	$99.90	$99.90
7 purchase totals =	$1,034.09		$1,113.7716	$1,113.77	$1,113.80	$1,113.70